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Low Back Pain: The Role of Fear

RESEARCH ARTICLE

The Back Belief Questionnaire is efficient toassess false beliefs and related fear in lowback pain populations: A transculturaladaptation and validation studyArnaud Dupeyron1,2*, Charlotte Lanhers3, Sophie Bastide4, Sandrine Alonso4,Matthias Toulotte1, Claire Jourdan5, Emmanuel Coudeyre3,6

1 Service de Medecine Physique et de Readaptation, Centre Hospitalier Universitaire de Nımes, Nımes,France, 2 EuroMov, Universite de Montpellier, Montpellier, France, 3 Departement de Medecine Physique etde Readaptation, Centre Hospitalier Universitaire, Clermont-Ferrand, France, 4 Departement deBiostatistique, Epidemiologie, Sante Publique et Informatique Medicale (BESPIM), Centre HospitalierUniversitaire de Nımes, Nımes, France, 5 Departement de Medecine Physique et de Readaptation, CentreHospitalier Universitaire Lapeyronie, Montpellier, France, 6 INRA, Unite de Nutrition Humaine (UMR 1019),CRNH Auvergne, Clermont-Ferrand, France

* [email protected]

Abstract

Background

According to the fear avoidance model, beliefs and thoughts can modify the outcome of

patient with low back pain. The Back Belief Questionnaire (BBQ)–a 14 items scale–

assesses these consequences of low back pain.

Objective

To test the psychometric properties of the French version of the BBQ.

Methods

The BBQ was translated using the forward–backward translation process. Throughout three

repeated evaluation time points (D1, D7 and D30), various aspects of validity were ana-

lysed: acceptability, quality of items, unidimentionality, internal consistency, temporal stabil-

ity (between D1 and D7), responsiveness (between D7 and D30), and construct validity

comparing it to other validated scales.

Results

One hundred and thirty-one patients were enrolled and 128 were analyzed. The acceptabil-

ity and the quality of the items were excellent. The scale was unidimensional and reliable

(internal consistency: Cronbach’s α = 0.8). The responsiveness was moderate but in line

with other scores. The BBQ was, as expected, convergent with day-to-day activities and

fear avoidance (FABQ and Tampa), disability (Quebec and Dallas scores), or anxiety and

depression (HAD); and not correlated with pain. Best correlations were found with Tampa

PLOS ONE | https://doi.org/10.1371/journal.pone.0186753 December 6, 2017 1 / 13

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OPENACCESS

Citation: Dupeyron A, Lanhers C, Bastide S, AlonsoS, Toulotte M, Jourdan C, et al. (2017) The BackBelief Questionnaire is efficient to assess falsebeliefs and related fear in low back painpopulations: A transcultural adaptation andvalidation study. PLoS ONE 12(12): e0186753.https://doi.org/10.1371/journal.pone.0186753

Editor: Terence J. Quinn, University of Glasgow,UNITED KINGDOM

Received: December 8, 2016

Accepted: October 6, 2017

Published: December 6, 2017

Copyright: © 2017 Dupeyron et al. This is an openaccess article distributed under the terms of theCreative Commons Attribution License, whichpermits unrestricted use, distribution, andreproduction in any medium, provided the originalauthor and source are credited.

Data Availability Statement: All relevantinformation are within the paper and its SupportingInformation files.

Funding: This research was funded by theUniversity Regional Hospital Caremeau, Nımes,France, Grant Number: Local/2010/AD-02. Thefunder had no role in study design, data collectionand analysis, decision to publish, or preparation ofthe manuscript.

https://doi.org/10.1371/journal.pone.0186753

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and FABQ. The temporal stability (test-retest reliability) was poor. However, similar changes

were observed in near conceptual score (FABQ), which confirmed that clinical status may

have not been stable and suggesting sensitivity to early changes for BBQ.

Conclusions

The BBQ showed good psychometric properties to assess false beliefs and related fear in

French or English LBP populations and can be used either for evaluation in international tri-

als or as a part of self-care training.

Introduction

According to the bio-psychosocial model, the course of chronic low back pain (CLBP) iswidely influenced by emotional, cognitive and behavioral factors [1]. It is well known that cor-tical processes are involved in the integration of multidimensional aspects of pain. This high-lights the shift from mechanical to functional response and leads to cognitive and behaviouraladaptation when pain persists. Therefore, patients may adopt individual strategies dependingon expectations, fears, and beliefs [2]. There is increasing evidence that beliefs as well asthoughts are widely altered in LBP patients [3] but also in physicians [4]. It is also clear thatbeliefs can change the way that patients struggle for recovery and autonomy [5].

Symonds et al. have developed a specific self-reported questionnaire–the Back Beliefs Ques-tionnaire (BBQ)–designed to explore beliefs and thoughts related to low back pain [6]. Unlikethe Fear Avoidance Beliefs Questionnaire (FABQ) score, which explores beliefs related to con-sequences of LBP on physical and work activities avoidance, the objective of the BBQ is todetermine the presence of various inevitable consequences of LBP in patient’s future among 14determinants. The first validation of the English version only comprised reliability and consis-tency in individuals and workers and showed that BBQ was able to distinguish workers withfalse beliefs associated with longer work absenteeism [6]. The BBQ seems to be used in prac-tice, usually in self-care and multidisciplinary programs probably as far as an evaluation (seek-ing false beliefs) or educational tool (treating false beliefs) [7]. However, this questionnaire hasnot been tested in non-worker LBP patients and likely needed more extensive validationprocess.

The aim of this work was to provide a French transcultural validated version of the BBQ.The study was divided into two steps: i) translation and cultural adaption of the BBQ and ii)validation of the French version in terms of acceptability, quality of the items, unidimensional-ity, internal consistency, temporal stability, responsiveness, and construct validity.

Method

The BBQ

Pain-related fear is known to affect daily activities and the development of disability as patientselaborate unsuitable representations of danger, either painful, crippling or destructive and theusefulness of the majority of treatments. Therefore, the items have been designed in order toexplore the degree of agreement of patients about developing various inevitable status relatedto LBP in the future. The questionnaire consists in a 14-item beliefs score. Nine items are usedfor the score (Q1, Q2, Q3, Q6, Q8, Q10, Q12, Q13 and Q14) and five are used as distractors(Q4, Q5, Q7, Q9 and Q11). The level of each belief ranks from total disagreement to total

BBQ validation and French adaptation


Competing interests: The authors have declaredthat no competing interests exist.


agreement on a Likert 5-level scale. The score obtained for each item is reversed (e.g. 5 means1 and 2 means 4) and nine items included in the total score are added. For each item, thehigher score means the worst future perceived (either illness perception or treatment effective-ness). For the entire BBQ, the higher the patient scores, the less he displays fear and false beliefs(as scores are reversed).

Translation

The BBQ was transculturally translated using the forward / backward procedure [8,9] ThreeFrench native bilingual physicians (AD, EC, AG) independently translated the questionnaire.They were asked to provide a global rather than word for word translation [10]. They reviewedeach translation together for cultural adaptations and obtaining a consensus version. A back-ward translation into English was then proposed by a native English translator (CS) to checkthe meaning of each item.

Population

Patients were eligible if i) they were consulting for back pain condition lasting more than 3months, ii) previous treatments (medications and/or physiotherapy) had been ineffective andiii) they had no previous history of surgery or multidisciplinary rehabilitation program or ded-icated educational intervention. All patients signed an informed consent. The study wasapproved by the regional ethics committee (Comite de Protection des Personnes Sud Mediter-ranee III, 2011.06.05), recorded by French authorities (RCB ID n˚ 2011-A00270-41 deliveredby AFSSAPS), and declared on Clinical trials (NCT01389999).

Study design

To validate the French version of the BBQ, this questionnaire was included in a multidimen-sional evaluation of CLBP integrated in rehabilitation programs provided by two tertiary careUniversity Hospitals. The questionnaires were filled out on the day of enrolment (D1), on thefirst day of the rehabilitation program (D7) and one month after the end of the rehabilitationprogram (D30). No treatment or intervention was scheduled between D1 and D7. The D30session aimed at controlling the beliefs’ changes if any.

Objective of the study: Validation of the translated BBQ

The validation process consisted in the assessment of the i) acceptability of each item and ofthe global questionnaire; ii) quality (absence of saturation, ceiling or floor effect, and redun-dancy) of each item and of the global questionnaire; iii) unidimensionality of scale; iv) internalconsistency; v) temporal stability using a test-retest reliability method between D1 and D7 instrictly the same conditions; vi) responsiveness between D7 and D30; and vii) construct valid-ity using correlations with other validated questionnaires exploring different dimensions toassess convergence and divergence.

The other validated questionnaires used were: the FABQ for fear and avoidance [11,12], theQuebec scale for disability [13], HADs for anxiety and depression [14], the Tampa for kinesio-phobia [15], Visual analogue scale (VAS) for the pain, and the Dallas pain questionnaire forday-to-day activities [16]. At D1 only the BBQ, Tampa, Quebec and FABQ were recorded inorder to control for changes in close concepts (fear and kinesiophobia), all questionnaireswere administered at D7 and D30.




Statistical analysis

Acceptability was assessed by the number and the proportion of the overall and for each itemabsence of responses (coted “no”). Acceptable items have to provide a proportion of “no”responses lower than 5%, if the proportion is higher than 10% the item is disputable.

Quality of items was assessed by the absence of saturation for each of them: ceiling or flooreffect and by the absence of redundancy between items evaluated by the nonparametric Spear-man rank correlation coefficient (with its 95% confidence interval, CI 95%) [17]. Spearmancorrelations above 0.9, between 0.7 and 0.9, between 0.5 and 0.7, between 0.3 and 0.5 andbelow 0.3 were considered as excellent, good, moderate, poor, and negligible.

Unidimensionality of the scale was assessed using the Mokken Scale Procedure (MSP) [18].The MSP aims at automatically partitioning the items into one or several sets by defining thedimensions of the scale and possibly a set of unscalable items using Loevinger H coefficients.

Internal consistency was estimated using the Cronbach’s α coefficient (CI 95%). A value ofthe score over 0.7 was considered reliable. The step-by-step Cronbach-α backward procedurewas used also to check the unidimensionality of the scale.

Temporal stability was assessed to control that the scale remained stable when clinical con-dition did not change. Test-retest reliability was assessed between D1 and D7. Stability of theglobal score was assessed using the intraclass correlation coefficient (ICC; CI 95%). ICC is con-sidered as excellent over 0.9, acceptable over 0.8, weak over 0.6 and inexistent below. The sta-bility of each item was assessed by the weighted kappa coefficient (K; CI 95%). K is excellentover 0.8, good over 0.6, medium over 0.4, poor over 0.2, bad over 0, inexistent below 0. TheBland & Altman graph method was used to evaluate the presence of a bias [19].

Responsiveness was assessed between D7 and D30 with the Cohen’s adjusted StandardisedResponse Mean (SRMa) [20] and tested using the Wilcoxon paired test. SRMa> 0.8,> 0.5,>0.2 and below are considered large, moderate, small and trivial, respectively.

Construct validity was assessed by searching convergence and divergence with otherdimensions assessed by other scales. Following the convergent hypothesis, a low BBQ (lowknowledge about LBP) was expected to match with high FABQ or TAMPA scores (high fearleading to movement and activities avoidance) and high Quebec or Dallas scores (high disabil-ity). On the other hand, in a divergent hypothesis, the BBQ would likely not be correlated withHAD (anxiety or depression) and VAS (pain). This validity was measured using the nonpara-metric Spearman rank correlation coefficient (CI 95%).

Supplementary analyses: A parametric item response theory (IRT) model was used to char-acterise the BBQ scale properties such as difficulty and discrimination of each item [21]. Allthe analyses were performed using SAS software version 9.4 (SAS Institute Inc., Cary, NC).

Results

Translation

The French version of the BBQ (S1 Appendix) was not different in structure from the originalversion. No cultural adaptation was necessary and only minor adaptations were made. Thefinal version was sent to one of the authors of the original BBQ (A.K. Burton) who gave a feed-back with the translated version and confirmed that the translated version and the English ver-sion explored the same dimension.

Population

Overall 131 patients were enrolled in the study: 128 patients at D1 (Centre 1, 105; Centre 2,23), 121 at D7 (103/18) and 101 at D30 (96/5) (Fig 1). Mean age at inclusion was 43.6 ± 10.1




(range 23–68), 62 (48%) were female, median duration of LBP was 49 months (range 3–400;inter-quartile range 18–133). LBP population’ characteristics are detailed in Table 1.

Fig 1. Flow chart.

https://doi.org/10.1371/journal.pone.0186753.g001

Table 1. LBP characteristics of the study population at the reference visit (D1).

Missing values Median Range IQR

Pain (0–100) 15 44 0–100 35–52

FABQ (0–66) 1 39 4–66 26–51.5

� Physical activity (0–24) 0 15 0–24 11–18

�Work (0–42) 1 26.5 0–42 13.5–35.5

Tampa (0–68) 5 45 21–66 38–49

Quebec (0–100) 1 36 3–82 23.5–52

Dallas (%)

� Daily activities 0 55.2 22.2–84.6 46.2–64.8

�Work-Leisure activities 1 54.5 7–94 40–67

� Anxiety-Depression 0 40 0–100 25–60

� Social interest 0 34 0–87 14–54

BBQ (0–45) 0 24 10–41 19–28

HAD

� Anxiety (0–21) 2 10 3–21 7–13

� Depression (0–21) 2 7 1–18 4–10

https://doi.org/10.1371/journal.pone.0186753.t001






Testing the questionnaire

Regarding acceptability for the BBQ tests, most of the BBQ collected were completed and only0.43% of all items were not filled (21/4858). A moderate ceiling effect was found for the itemsQ2 (32%), Q3 (36%) and Q6 (54%) as most of patients scored highest level and a floor effectfor the item Q8 (60%) as most of patients did not believed that they would be, one day, forcedto use a wheelchair because of their back pain. Nor floor neither ceiling effect was detected forthe global score. Correlations between items were very low or absent (Spearman < 0.5) show-ing no redundancy between items.

One unique dimension was defined by the MSP confirming the unidimentionality of theBBQ scale. However, two items (Q1 and Q8) did not satisfy the cut-offs for the Loevinger Hcoefficient and were not selected by the MSP in the unique dimension of the scale.

Global Cronbach α coefficient was 0.8 (0.7–0.8) and above the 0.7 cut-off for reliable inter-nal consistency. The step-by-step Cronbach α backward procedure confirmed the generalagreement between items measuring the same construct (Fig 2). The graphical representation

Fig 2. Step-by-step Cronbach α backward procedure according the number of items. The items were successively removed according the followingorder: Q8, Q1, Q13, Q12, Q3, Q10, Q2 (remaining Q6 and Q14).






obtained at the end of the Cronbach α procedure is monotone increasing, which reflects agood reliability of all items. The BBQ does not have any items causing a decrease of the curve.This confirms the results from the factor analysis for unidimensionality.

Temporal stability was low between measures performed at D1 and D7 with a 0.64 ICC (CI95%; 0.52–0.73) for the global scale and a K varying from 0.24 (0.11–0.38) to 0.46 (0.35–0.57)for each item. The Bland & Altman graph (reported in Fig 3) shows the existence of a bias of+1.24 meaning an improvement of the beliefs already at D7. BBQ scores at D1 and D7 were21 [18–27] (median, IQR) and 24 [19–28] respectively (p = 0.01). No difference was foundbetween centre, gender and back pain duration between visits to explain this poor temporalstability. A change in FABQ between D1 and D7 was also found (44 [28–54] and 39 [26–51],respectively (p = 0.03)) whereas Tampa scores were not different (p = 0.87). Therefore, bothBBQ and FABQ scale’s score changed significantly for the same subset of patients.

The responsiveness to the BBQ was moderate and coherent with the other scores, as shownin Table 2.

Fig 3. Bland & Altman method representation of a bias in the test-retest reliability method to assess temporal stability between D1 and D7. Abias between the mean differences can be detected. Here the score calculated at the second visit is +1.24 higher.






The construct validity was estimated at D7 for all variables. Consistently with the divergenthypothesis, there was no correlation with pain (r = -0.15, p = 0.19). Regarding the convergenthypothesis, the BBQ was best correlated with the Tampa (r = -0.66, p<0.001) and the FABQ(r = -0.52, p<0.001). Correlations with disability scales were poor (Quebec, r = -0.31, p<0.001;Dallas, r = -0.24 to -0.43, p<0.01). Oppositely to the divergent hypothesis, the BBQ scale wascorrelated, although weakly, with HADs depression (r = -0.42, p<0.001) or anxiety (r = -0.28,p = 0.0017).

According to the parametric IRT model results, the most discriminative items of the scalewere the items 14 and 6, and the less discriminative the items 1 and 8, which were indeed theless difficult items. The information curves obtained by the parametric IRT model are pre-sented in Fig 4.

Discussion

Overall, this study shows that the French version of the BBQ has good psychometric propertiesand can be used for evaluation of thoughts, knowledge and beliefs in patients with LBP. Thetranslation process required only vocabulary changes with a questionnaire easily comprehensi-ble and well accepted by patients. This aspect of low back pain is very important to addresssince the fear avoidance model widely explains how false beliefs and wrong thoughts contrib-ute to wrong outcome [22].

What the study adds

In addition to the extension of the BBQ use in French, this study brings additional knowledge.Indeed, although the construct validity, internal consistency or temporal stability have alreadybeen explored, characteristics such as quality of items and responsiveness have not been previ-ously analysed. However, populations enrolled in previous studies were not necessarilyinvolved in long term disability related to low back pain, usually screened for rehabilitationand education multidisciplinary programs. The population targeted in the present study givesa more accurate picture of LBP patients with severe disability related to beliefs.

Overall, the BBQ is well accepted (0.43% of no-responders) with no floor or ceiling effectdetectable for the global score, neither redundancy between items (weak to very weak correla-tion between items, spearman < 0.5). This can explain the low rate of non-responders (14.3%for Bostick et al.) [23] or missing data (13.5% for Symonds et al.)6 described elsewhere. How-ever, researchers should pay attention to items’ ceiling effect (Q2, Q3 and Q6), resulting in apoor discriminating ability to detect some specific LBP patients’ beliefs as most of them con-sider that back pain will mean pain for the rest of their life (Q3), will limit daily life activities(Q2) or work to some individual extend (Q6). Conversely, Q8 demonstrated a floor effect as

Table 2. Responsiveness of the BBQ compared to different scores before and after the rehabilitation procedure.

n Before rehabilitation Median [IQR] After rehabilitation Median [IQR] p Cohen’s adjusted SRM

FABQ total (/66) 96 39.0 [26.6–50.5] 28.0 [14.5–42.0] <0.0001 0.81

Physical Activity (/24) 16.0 [12.0–19.0] 7.0 [2.0–13.0] <0.0001

Work (/42) 25.5 [13.0–35.5] 19.5 [8.5–34.0] <0.0001

Tampa (/68) 92 45.0 [38.5–50.0] 36.0 [30.0–43.0] <0.0001 0.98

Quebec (/100) 98 34.0 [22.0–48.0] 20.5 [12.0–38.0] <0.0001 0.94

BBQ (/45) 100 23.5 [18.5–28.0] 27 [22.5–32.5] <0.0001 -0.7

(IQR: inter-quartile range)






most patients do not belief that back pain will lead to severe impairment. However, thisthought, usually reported in educational assessment, is probably used by patients to test physi-cians’ opinion but cannot objectively be considered as a false belief. As a consequence, theinterpretation of such item factor components must be careful.

The correlation between the nine items was good (Cronbach’s coefficient = 0.8; Fig 2) asfound by others [6,23] confirming the good internal consistency. Each item seems to evaluate

Fig 4. Item information curves of the nine items used for scoring the BBQ scale obtained by the parametric IRT model. Items1, 8, 12 and 13 have a low power of information over the entire scale. These items contributed very little to the ranking of individuals.Conversely, the strongest informations power were observed for items 6 and 14. The minimal anonymized data set of the presentstudy is available in S2 Appendix.






the same construct with α coefficient always over 0.7 and still stable after each deletion withoutany significant redundancy between items.

Comparison to other scores

The concept that fear and beliefs lead to movement and activities avoidance, disability, andtherefore inevitable consequences of low back pain, according to the fear avoidance model[24] was believable. As expected, the BBQ was convergent with others scales which have closeconcepts such as Tampa for kinesiophobia and FABQ for fear avoidance of work and physicalactivity (spearman coefficient >0.5; p<0.001). This association was higher than regardingfunctional scales: for example, the relationship with the Quebec scale was weaker but still sig-nificant (spearman coefficient <0.5; p<0.001).

Unexpectedly, disability and depression, explored with Dallas and HAD scales were conver-gent with BBQ although weakly (spearman coefficient <0.5; p<0.01). However, the linkbetween HAD (anxiety part) and Tampa scale [25] or FABQ and HAD [12,26] can explainsuch a relation.

Therefore, the BBQ gives clinicians some new information that are probably not providedelsewhere considering the weak or inexistent correlations observed with other scores.

In a previous study, Bostick et al. [23] have tested the relationship between beliefs and his-tory of low back pain. However, the results suggested that beliefs were not exclusively linked topain. This is confirmed by the divergence of BBQ with pain evaluation. Fear can lead to pain(Montaigne; “He who fears shall suffer, already suffers what he fears”) but does not explain orencompass pain. Finally, the best correlations observed with Tampa and FABQ were expectedsince fear of movement and avoidance are conceptually close [26–28]. Therefore, in a non-worker LBP population, the BBQ can be easily used and interpreted in this frame.

Finally, for the first time the responsiveness of the BBQ after an educational and rehabilita-tion program has been tested. In most cases, beliefs improve after multidisciplinary interven-tions and accordingly the BBQ score increases after one week of educational intervention (4.5points increasing; p<0.0001). The BBQ score can therefore be used as an objective tool of edu-cation assessment in CLBP. Furthermore, associated with a rehabilitation intervention, theBBQ was able to detect changes accordingly with other scales testing avoidance of movement,return to work, kinesophobia or and functional abilities as reported here (Table 2).

Limitations

Temporal reliability tests have shown that test-retest reliability between D1 and D7 was eitherweak or poor according to definition. This can be unexpected since no intervention was sched-uled during this period. Two hypotheses may explain this result. First, it could be suspectedthat the BBQ is not stable with time and probably variable whereas the clinical status is stable;however, this hypothesis requires confirmation that no clinical change has occurred. Second,it can be suspected that the patient educational assessment proposed at inclusion (D1) hasalready modified the related beliefs. The changes observed on the FABQ scores between D1and D7 pleads this reason. Moreover, FABQ have demonstrated a good temporal stability [26,27]. Since educational interventions modify beliefs in LBP population [29–31], changes in theBBQ and another score would rather support the sensitivity to change of BBQ. In this study,patients, were enrolled because of chronic LBP and were evaluated the same day of the inclu-sion. It is possible therefore that the educational questioning provided the first day would haveled to changes in back pain thoughts because of the discussions with the team and/orexchanges between participants. This hypothesis however, needs to be confirmed by studieswith no educational assessment.




Finally, data on the professional status of the patients included was not specified so we arenot able to extrapolate our results to the general LBP population.

Perspectives

The use of the BBQ score for evaluation of inevitable consequences of beliefs related to LBPand educational assessment seems of interest. However, the usefulness of the whole set ofitems could be questioned. Bostick and colleagues [23] have already underlined the littlechange in the overall score whether Q1 remained or not (correlation still very high and reli-ability unchanged). Similarly, in the present study, the interest of Q1 as well as Q8 were disput-able. Indeed, these two items were not selected in the MSP, they demonstrated the weakestinput for internal consistency and they were the less discriminative item in the IRT model.Therefore, it could be interesting to test the validity of the BBQ using only “loading items” forscoring and propose another form of the questionnaire. Nevertheless, the distractors are inter-esting in an educational perspective. Indeed, the BBQ is typically oriented toward emotions,thoughts and beliefs assessment and can be easily used as educational support. Each itemexplores most of the questions asked by LBP patients (e.g. “back trouble will stop you fromworking” or “means you end up in a wheelchair”) and can open a face-to-face discussion onindividual worst beliefs. In this perspective, the BBQ may enhance their ability to catchunpleasant but still vague related thoughts for a better understanding and management [7,24].

Conclusion

The BBQ, now available in French language, showed good psychometric properties to assessfalse beliefs and related fear in French LBP populations. These results suggest that the ques-tionnaire can be used either for evaluation in international trials or as a part of self-caretraining.

Supporting information

S1 Appendix. The French version of the Back Belief Questionnaire.(TIFF)

S2 Appendix. Minimal anonymized data set used for BBQ validation.(PDF)

Acknowledgments

The authors would like to thank Mariella Lomma for her final editing contribution, Dr TonyGelis (French to English) and Carey Suehs (English to French) for their contribution to thetranslation procedure of the questionnaire and all the clinicians involved in this study for thetime donated.

Author Contributions

Conceptualization: Arnaud Dupeyron, Emmanuel Coudeyre.

Data curation: Arnaud Dupeyron, Charlotte Lanhers.

Formal analysis: Arnaud Dupeyron, Sophie Bastide, Sandrine Alonso, Matthias Toulotte,Emmanuel Coudeyre.

Funding acquisition: Arnaud Dupeyron.

Investigation: Arnaud Dupeyron, Charlotte Lanhers.



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Fear of Movement Is Related to Trunk Stiffness in LowBack PainNicholas V. Karayannis1, Rob J. E. M. Smeets2, Wolbert van den Hoorn1, Paul W. Hodges1*

1 The University of Queensland, NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences, Brisbane,

Australia, 2 Department of Rehabilitation Medicine, Research School CAPHRI, Maastricht University and Adelante Centre of Expertise in Rehabilitation and Audiology,

Hoensbroek, The Netherlands

Abstract

Background: Psychological features have been related to trunk muscle activation patterns in low back pain (LBP). Wehypothesised higher pain-related fear would relate to changes in trunk mechanical properties, such as higher trunk stiffness.

Objectives: To evaluate the relationship between trunk mechanical properties and psychological features in people withrecurrent LBP.

Methods: The relationship between pain-related fear (Tampa Scale for Kinesiophobia, TSK; Photograph Series of DailyActivities, PHODA-SeV; Fear Avoidance Beliefs Questionnaire, FABQ; Pain Catastrophizing Scale, PCS) and trunk mechanicalproperties (estimated from the response of the trunk to a sudden sagittal plane forwards or backwards perturbation byunpredictable release of a load) was explored in a case-controlled study of 14 LBP participants. Regression analysis (r2)tested the linear relationships between pain-related fear and trunk mechanical properties (trunk stiffness and damping).Mechanical properties were also compared with t-tests between groups based on stratification according to high/lowscores based on median values for each psychological measure.

Results: Fear of movement (TSK) was positively associated with trunk stiffness (but not damping) in response to a forwardperturbation (r2 = 0.33, P = 0.03), but not backward perturbation (r2 = 0.22, P = 0.09). Other pain-related fear constructs(PHODA-SeV, FABQ, PCS) were not associated with trunk stiffness or damping. Trunk stiffness was greater for individualswith high kinesiophobia (TSK) for forward (P = 0.03) perturbations, and greater with forward perturbation for those withhigh fear avoidance scores (FABQ-W, P = 0.01).

Conclusions: Fear of movement is positively (but weakly) associated with trunk stiffness. This provides preliminary supportan interaction between biological and psychological features of LBP, suggesting this condition may be best understood ifthese domains are not considered in isolation.

Citation: Karayannis NV, Smeets RJEM, van den Hoorn W, Hodges PW (2013) Fear of Movement Is Related to Trunk Stiffness in Low Back Pain. PLoS ONE 8(6):e67779. doi:10.1371/journal.pone.0067779

Editor: Sam Eldabe, The James Cook University Hospital, United Kingdom

Received October 8, 2012; Accepted May 27, 2013; Published June 27, 2013

Copyright: ! 2013 Karayannis et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permitsunrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: NK is supported by a PhD scholarship from The CCRE SPINE, The University of Queensland International Research Tuition Award and the AmericanAcademy of Orthopaedic Manual Physical Therapists - Cardon Grant Award. PH is supported by a Senior Principal Research Fellowship from the National Healthand Medical Research Council of Australia. The authors have no financial or personal relationships with other people or organisations that could inappropriatelybias their work. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

* E-mail: [email protected]

Introduction

People with low back pain (LBP) have changes in muscleactivation [1,2], trunk mechanical properties [3,4]) and fear ofpain [5,6]. Although biological and psychological domains areoften discussed in isolation, they are likely interdependent.Consistent with this view, studies have shown that adaptation inmuscle activation depends on attitudes about pain [7], andcompromise of the expected relaxation of the lumbar muscles attrunk flexion end range in people with LBP correlates with highfear avoidance behaviour [8]. Although it is assumed changes intrunk muscle activation relates to differences in trunk mechanicalproperties, the association between variation in psychologicalpresentation and trunk mechanical behaviour has not been tested.

A relationship between psychological and mechanical featureswould support contemporary neurophysiology and psychologypain models, for example, the prediction of pain/threat of injurycauses the body to protect the painful part in an effort to reducepain [9], the fear-avoidance model [10,11], and the diathesis-stresspain theory [12] (i.e., behaviours which provide short-term reliefcan have detrimental long-term effects if the behaviour remainsunchanged [13]). We considered simultaneous investigation ofbiological and psychological systems could help to betterunderstand this relationship between mechanical and behaviouraldomains.

Investigation of how biological and psychological featuresinteract is of relevance because they both have the potential toinfluence the presentation and management of LBP. Motor

PLOS ONE | www.plosone.org 1 June 2013 | Volume 8 | Issue 6 | e67779

control (i.e., trunk stiffness, relative tissue flexibility, preferredmovement strategies) and psychological factors (i.e., emotions,cognitions, behaviours) are both likely to influence motor outputand alter trunk mechanical behaviour. Depending upon therobustness of ‘motor’ and ‘psychological’ systems, it is probable therelationship is bi-directional in nature. Optimal trunk mechanicalperformance will vary depending upon the required task, and if aperson with LBP cannot efficiently alter their mechanical response,it may have negative long-term biopsychosocial consequences (i.e.,increased trunk load, reduced movement variability, reinforce-ment of maladaptive pain behaviour).

Several psychological features have been explored in relation toLBP, most notably dimensions related to the fear-avoidance model[14]. The three aspects of this model are fear of movement/re-injury, pain catastrophizing [15], and avoidance behaviour, all ofwhich could relate to changes in trunk motor control. Question-naires to assess these components have been developed [16–19].There has also been a focus on distress [20,21]. It remainsunknown which psychological features, if any, are related to trunkmechanical properties. In this study we aimed to test thehypothesis that higher kinesiophobia relates to greater protectionof the spine (increased trunk stiffness) by exploring the relationshipbetween trunk mechanical properties and other aspects of the fear-avoidance model (pain catastrophizing thoughts, avoidancebehaviour) as well as a component of the distress model(depression).

Methods

ParticipantsNineteen participants with LBP (6 male, 13 female; mean

body mass index (BMI) 23.6 (SD 3.8); mean age 43 (range 26–65 years)) were recruited with the objective to include thosewith both high and low fear of pain. Participants were includedif they scored at least a 10 out of 100 on the Quebec Back PainDisability Scale (QBPDS), reported a pain intensity of at least1/10 at the time of participant screening (Numeric Pain RatingScale, NPRS), and a BMI of #31. Exclusion criteria were ahistory of cancer, unexplained weight loss .4.5 kg in the past 6months, neurologic disease, severe spinal structural deformity(e.g., .8 mm rib hump), loss of bowel or bladder control, majorchanges in walking balance or strength, numbness or alteredsensation in the groin region, respiratory disease, hip or kneesurgery or currently had a hip or knee injury, use of a walkingaide, numbness in their lower extremities, or pregnancy.Participants were recruited via university and city newspaperadvertisements. The Institutional Medical Ethics Committee atthe University of Queensland approved the study and partic-ipants provided written informed consent.

ProcedurePsychological dimensions. Participants completed ques-

tionnaires to evaluate the psychological features of their LBP.These were: Tampa Scale for Kinesiophobia (TSK), Photographseries of Daily Activities-Short electronic Version (PHODA-SeV),Fear Avoidance Beliefs Questionnaire (FABQ), Center forEpidemiological Studies-Depression Questionnaire (CES-D), PainCatastrophizing Scale (PCS), Numeric Pain Rating Scale (NPRS),and Quebec Back Pain Disability Questionnaire (QBPDQ). .

The TSK [17] is a 17-item measurement of fear of movement/(re) injury (1 ‘Strongly disagree’ to 4 ‘Strongly agree’) and has goodreliability and validity [5]. The PHODA-SeV [19] is a valid andreliable measure of perceived harmfulness of physical activity (0‘Not harmful at all’ to 100 ‘Extremely harmful’) in patients with

chronic LBP [19]. To gather a better comparison of the basicmovement categories portrayed in the PHODA-SeV and theexperimental tasks that would be performed by the participants,an additional component was added to the PHODA-SeV thatinvolved a photograph and explanation of the experimental trunkperturbation task (see below) (Photograph of Experimental Task[PHOET]) (Figure 1). Participants rated their perceived harmful-ness of participating in this task according to the same‘harmfulness thermometer’ used in the PHODA-SeV before andafter completing the test.

The PCS [18] is a 13-item questionnaire that reliably measuresthoughts and feelings related to pain which suggest catastrophicthinking [22]. The FABQ [16] measure avoidant behaviour with16 items that measure the agreement of statements related toPhysical Activity (FABQ-PA) and Work (FABQ-W) affecting theparticipant’s LBP, and is a valid and reliable measure of fear-avoidance constructs for ‘chronic’ LBP patients [22].

The CES-D contains 20 items related to how often theperson has felt depressed during the last week. It has highsensitivity (81.8%) and specificity (72.7%), and good predictivevalidity among ‘chronic’ pain patients for measurement ofsymptoms of depression [23]. The QBPDS [24] is a 20-itemquestionnaire related to how back pain affects a person’s dailylife (0 ‘Not difficult at all’ to 5 ‘Unable to do’). The NPRS [25](0 ‘No Pain’ to 10 ‘Worst imaginable pain’) was administered atthe time of recruitment, before the experimental task, andimmediately following the experimental task. Measures of pain(NPRS) and the PHOET were preformed at the start of thetesting session and after completion of mechanical testing.

Mechanical dimensions. Mechanical properties of thetrunk were evaluated from the response of the trunk to asudden perturbation [3] (Figure 1). Participants sat in a semi-seated position with the pelvis stabilized by a belt and low-levelbackrest. They were instructed to sit in their normal preferredposture. A chest harness was placed over the participant’sshoulders and adjusted so that the attached cables wereapproximately at the trunk’s center of mass (T9). Cables wereattached to equal weights (7.5% body weight) by electromagnetsand passed over low-friction pulleys. A marker was placed onthe cable to serve as a guide to ensure consistent posturebetween trials. Because front and back loads were equal,minimal muscle activity was required to hold the trunk upright.A load was randomly released from the front (x20) or back

Figure 1. Experimental set-up. Participants sat in a semi-seated,upright posture with the pelvis fixated by a belt. The load was releasedfrom one side of the trunk by release of an electromagnet.doi:10.1371/journal.pone.0067779.g001

Kinesiophobia Is Related to Trunk Stiffness in LBP


(x20) by deactivation of one electromagnet. Participants wereinstructed to return to their starting position after eachperturbation. The dropped weight was re-attached, andsuccessive drops followed every ,5 s until completion of thetrial (,15 min).

Transducers (Futek Advanced Sensor Technology, Inc., Irvine,CA, USA) between the weights and trunk measured force. Forcedata were sampled at 200 Hz using a Power 1401 data acquisitionsystem and Signal software (Cambridge Electronic Design, Cam-bridge, England). Data were exported and analyzed using Matlab(Mathworks, Natic, MA, USA).

Data AnalysisTrunk ‘stiffness’ is the body’s ability to resist displacement and is

the sum of passive (osseoligamentous system) and active (neuro-muscular system) properties [26]. Trunk ‘damping’ is the body’sability to resist velocity. Stiffness and damping were estimatedusing a second order linear model (Equation 1) based on theapplied force and resultant trunk kinematics, from the time ofweight release until maximum trunk displacement.

F~m€xxzB _xxzKx ð1Þ

Where F is the resultant force vector on the trunk €xx, _xx and x arethe acceleration, velocity, and position vectors of the trunk,respectively. F was calculated by subtracting back from frontforce. €xx was calculated from the force transducer attached to theunreleased weight, and was numerically integrated to calculate _xxand x. As m(effective mass), B (effective damping), and K (effectivestiffness) were assumed to be constant, the standard least squaresprocedure was used to solve the estimation. To increase theprocedure’s robustness, data for the second-order linear equationwere numerically integrated twice [27]. Modeled data werechecked for validity by fitting a regression line between themodeled and recorded displacement data. Data were excludedfrom the analysis if the correlation coefficient was less than 0.97.This was identified for data from 2 participants.

To ensure normal distribution, data were transformed ifShapiro-Wilk and Shapiro-Francia test for normality was signif-icant (P,0.05). The appropriate data transformation (logarithm,square root or inverse) was based on the best normal datadistribution tested with skewness and kurtosis test for normality.Regression analysis was performed to test the linear relationshipsbetween trunk mechanical properties (trunk stiffness and damping)to both forward and backward perturbations and psychologicalfactors (questionnaire scores). As an additional exploratory analysisand to provide additional support for any relationships identifiedin the regression analysis, data were stratified into groups with lowand high scores for each psychological measure (divided bymedian values). The approach of using the median value or othercut-off values to divide the population based on their response toquestionnaires (i.e., TSK) have been used in previous studies todescribe the data [28,29]. Mechanical variables were comparedbetween groups with t-tests for independent samples. As data forthis secondary analysis was performed in an exploratory mannerfor further interpretation of regression analyses, a Bonferronicorrection was not used as this was considered too conservative inthis hypothesis-driven context [30]. NPRS and PHOET werecompared between pre- and post-test measures with t-tests fordependent measures. Significance was set at P,0.05. Data arepresented as mean and standard deviation (SD) throughout, unlessstated otherwise.

Results

Mean, range, and median values for TSK, PHODA-SeV,FABQ-W and PA subscales, PCS, CES-D, QBPDS, NPRS, age,and symptom duration are presented in Table 1. Table 2 providescomparison of normative values for participants with LBP in thisstudy (which were lower) and 4 other studies [29,31–33]. Table 3provides a comparison of group data for trunk mechanicalvariables in this study and existing data [3] which used similarmethods. Data for five participants were excluded from analysisdue to either technical difficulties with data recording (n = 3) orfailure of modelled data to adequately fit the recorded data oftrunk mechanical properties (n = 2). There was a positive linearassociation between kinesiophobia (TSK) and trunk stiffness inresponse to a forward perturbation (r2 = 0.33, P,0.03, Table 4,Figure 2). Further exploratory analysis of participants split into‘high kinesiophobia’ and ‘low kinesiophobia’ groups based on themedian TSK value (score of 38), showed higher trunk stiffness inresponse to forward perturbation for those with higher TSK(P = 0.03, Figure 3) but not backward perturbation (P = 0.15)(Table 5). Likewise, when participants were split into ‘high’ and‘low’ fear avoidance groups according to the median FABQ –Wand PA values, trunk stiffness was significantly greater for the‘‘high’’ than ‘‘low’’ group during forward perturbations for theFABQ-Work subscale (P = 0.00). Trunk stiffness (high/low) groupsfor the forward perturbation were not significantly different basedon scores from the FABQ-Physical Activity subscale (P = 0.06), norwere trunk stiffness groups significantly different during backwardperturbations (Table 5). There was no significant correlationbetween trunk damping and kinesiophobia (Table 5) or betweentrunk stiffness or damping and the other psychological measuresrelevant to the fear-avoidance model (PHODA-SeV, PCS). Thecontext-specific kinesiophobia measure that was related to theparticipant’s perceived harmfulness of the experimental task(PHOET) was not correlated with any mechanical property(Forward and backward stiffness P = 0.32 and 0.23, Forward andbackward damping P = 0.45 and 0.84, respectively). Further, othermeasures of depression (CES-D), disability (QBPDS), painintensity (NPRS) and age were not associated with trunkmechanical properties (Table 4). Pain was not worsened by testing(pre-test pain 2.7(2.1)/10 vs. post-test pain 2.6(2.3)/10), but theperceived harmfulness of the experimental task, as measured bythe PHOET, reduced from a pre-test value of 42(22.3)/100 topost-test value of 23.2(22.6)/100).

Discussion and Conclusion

This study provides partial support for the hypothesis thatpsychological aspects (i.e., kinesiophobia) are not independentfrom the biological presentation (i.e., trunk mechanical properties)of LBP. Consistent with our hypothesis, higher measures ofkinesiophobia (TSK) were associated with higher measures oftrunk stiffness in response to a forward perturbation. However,trunk damping did not correlate with psychological measures.When data were further probed by stratification into groups withhigher and lower scores on measures of psychological features,those with high measures of kinesiophobia (TSK) and fearavoidance beliefs (FABQ) had greater trunk stiffness in responseto forward perturbations. The observations of this study imply thatneither biology nor psychology should be considered in isolationfor investigation or management of this multidimensional disorder.

Despite the relationship between high trunk stiffness andkinesiophobia, trunk mechanical properties were not associatedwith pain-related fear measures, such as perceived harmfulness(PHODA-SeV, PHOET) or pain catastrophizing (PCS). Trunk



mechanical properties were also not associated with measures ofdisability (QBPDS) or depression (CES-D). Catastrophizing isproposed to initiate the fear-avoidance event cycle, and disabilityand depression are identified as consequences of elevated pain-related fear and avoidance. One interpretation of the present datais that biomechanical manifestations of pain (i.e., elevated trunkstiffness and increased superficial trunk muscle activity which islikely to contribute to the increased stiffness) are most closelyassociated at the pain-related fear stage of the fear-avoidancemodel, rather than its hypothesised precursor, catastrophization.

The basis for the significant association between mechanicalproperties and kinesiophobia, but not the preceding component ofcatastrophizing or resulting disability and depression is unclear.One possible explanation is that the proposed steps of the fear

avoidance model are non-linear, and there are other ways thehuman system responds to catastrophizing and disability, whichare not represented or manifested through these mechanicalbehaviors. Pain intensity and/or symptom duration could also playa role in reported fear-avoidance and distress levels, and it isimportant to acknowledge the relatively low pain intensity values(2.7/10 (2.1)), and persistent and recurrent symptom duration (9months) of the participants in this study.

The lack of significant relationship between biological proper-ties and the PHODA-SeV, PHOET, and PCS is perhaps reflectiveof the context or interpretation of the questionnaires. A plausibleexplanation for the correlation between TSK and trunk mechan-ical properties in the absence of relationship with the other fear-avoidance related questionnaires might be explained by widerconsideration of psychological variables in this measure. The TSKcontains items pertaining to a wide spectrum of beliefs (e.g., painwill increase or re-injury will occur if they increased their physicalactivity or exercise level; something is dangerously wrong with

Table 1. Group data for psychosocial variables.

Mean (SD) Range Median

TSK 36.3/68 (7.0) 23–49 38

PHODA-SeV 35.7/100 (14.2) 9.4–56.8 38.7

FABQ-W 13.2/42 (11.4) 0.36 12

FABQ-PA 11.9/24 (5.3) 3–20 11.5

PCS 14.4/52 (8.2) 3–31 13

CES-D 11.5/60 (11.5) 4–25 9.5

QBPDS 25.7/100 (13.8) 8–57 23

NPRS (Pre-Test) 2.7/10 (2.1) 0–6.5 2

PHOET (Pre-Test) 42/100 (22.3) 10–85 40

Age 43.4 (13.2) 27–65 40

Current episode duration(weeks)

35.8 (23.3) 1–60

TSK = Tampa Scale for Kinesiophobia, PHODA-SeV = Photographs of DailyActivities Short electronic Version, FABQ – W and PA = Fear Avoidance BeliefsQuestionnaire - Work and Physical Activity subscales, PCS = PainCatastrophizing Scale, CES-D = Center for Epidemiological Studies – Depressionscale, QBPDS = Quebec Back Pain Disability Scale, NPRS = Numeric Pain RatingScale, PHOET = Photograph of Experimental Task.doi:10.1371/journal.pone.0067779.t001

Figure 2. Correlation between TSK and trunk stiffness in response to (a) forward, and (b) backward perturbations.doi:10.1371/journal.pone.0067779.g002

Figure 3. Trunk stiffness for forward perturbation for individ-uals with high and low kinesiophobia (TSK) and fear avoidancebeliefs (FABQ). TSK = Tampa Scale for Kinesiophobia, FABQ-W = FearAvoidance Beliefs Questionnaire-Work subscale.doi:10.1371/journal.pone.0067779.g003



their LBP; they are at a greater risk of injuring themselves; painequates to injury or danger; and they are being delegitimized). Incontrast, FABQ items attempt to gain insight on: the heaviness ormonotonous behaviour of their work, normal work ability, returnto work expectancy, beliefs related to pain serving as an indicatorthat they should stop their activity, the belief that feeling painserves as an accurate measure that something is dangerouslywrong. Further, the PHODA-SeV (and PHOET) are merelyasking the participant to consider which activities they considerharmful or damaging to their back and the PCS primarily containsquestions related to catastrophizing/perseverating thoughts (e.g.,‘‘I keep thinking about how much it hurts’’) and questions relatedto fear, worry, and anxiety. It could also be that the psychometricvariables of the TSK are more sensitive to the particular measuresof motor control included here.

Clinical RelevanceAn interpretation of the results is that kinesiophobia is more

closely associated with trunk mechanical properties than otherpsychological factors (fear avoidance beliefs, pain catastrophizingthoughts, and depression). This finding highlights the interactionbetween kinesiophobia and trunk control as a potential target forfuture work addressing questions of causality and design ofinterventions.

Integration of a biopsychosocial perspective into the practice ofpain management is well accepted as the gold standard of care, butdisparity could arise if clinicians choose to focus effort on either abiomedical or psychological approach in isolation. The potentially

false rationale for incorporating this dualistic philosophy couldstem from a misleading judgement that either the mechanicalfactors or psychological factors are a stronger mediator of painand/or pain behaviour, and hence, only focus the interventionalong one of these domains. Another commonly held perspective isthat biomechanical intervention should be augmented withpsychological treatments only in cases where patients areconsidered to have a higher risk of involvement of psychologicalfactors in their presentation, but comprehensive identification ofthose individuals at higher risk remains a challenge. Results of thisstudy can be interpreted to suggest that neither domains should beconsidered in isolation, and supports the rationale to combinebiomechanical knowledge with psychologically informed principlesthroughout the assessment, treatment planning, and implementa-tion phases of pain management. This appears particularlyrelevant for those individuals who exhibit higher fear of pain/injury and avoidance behaviour.

LimitationsThe results of this study should be discussed with consideration

of several methodological limitations. In relation to the participantprofiles, measures related to kinesiophobia deserve discussion. TheTSK scores (36(7), range 23–49) were obtained from participants(n = 19) who were predominantly not seeking treatment for theirLBP. If TSK values from this study (Mean = 36.3 (7.0)) arecompared with TSK measures from other larger LBP studies[29,31–33], it is evident that our population, while perhaps moregeneralizable in terms of a more typical LBP population, does notrepresent a highly kinesiophobic or fear avoidance presentation.For example, in the Leeuw et al. study [29] participants wereexcluded if they held TSK scores ,34, whereas in this study only 9of the 14 participants had a TSK score .34. Furthermore, theFABQ median split values used in this study (FABQ-W = 12,FABQ-PA = 11.5) are well below proposed elevated cut-off values(FABQ-W .34, FABQ-PA .15) used in previous studies [34] toidentify individuals with high fear-avoidance beliefs. A furtherissue is that the participant sample size for this initial exploratorystudy (n = 19) may lack sensitivity to detect smaller effects. Afollow-up study with a larger sample size is required to apply morevigorous statistics (i.e., multiple linear regression analysis, Bonfer-roni correction) and draw more robust conclusions related to thispreliminary, exploratory finding. This is part of ongoing research.

Future DirectionsResults imply that trunk stiffness and kinesiophobia might serve

as important moderators and/or mediators of persistent and

Table 2. Reported values for Tampa Scale for Kinesiophobia(TSK) for people with low back pain.

StudyNumber ofparticipants TSK

Current study 19 36.3 (7.0)

Nicholas et al [31] 70 41.4 (9.0)

Smeets et al [32] 53586151

39.0 (6.5)38.7 (6.9)39.7 (7.1)37.8 (7.0)

Roelofs et al [33] 482 43.2 (8.4)

Leeuw et al [29] 85 42.0 (6.2)

doi:10.1371/journal.pone.0067779.t002

Table 3. Current and published data for trunk mechanical properties.

Forward Perturbation Backward perturbation

Study Damping (Ns/m) Stiffness (N/m) Damping (Ns/m) Stiffness (N/m)

Hodges et al [3]*

Low back pain Mean (SD) 17 (20) 1997 (474) 63 (39) 2035 (533)

Control Mean (SD) 55 (37) 1641 (376) 91 (34) 1814 (471)

Current study

Low back pain Mean (SD) 94 (69) 1556 (753) 194 (120) 2132 (1791)

Range 4–164 826–3775 8–325 554–7975

Median 88 1491 218 1654

*Data for the current study relate to a perturbation induced by a removal of smaller load than that used in the study by Hodges et al. [3].doi:10.1371/journal.pone.0067779.t003



recurrent LBP. This provides prioritization for future multi-system, biopsychosocial, and applied physiology investigativemodels to determine if pain management interventions aimed attargeting trunk mechanical properties and kinesiophobia reducepersistence or recurrence of LBP. Various movement based,cognitive and behavioural intervention strategies are worthy ofinvestigation. The relationship between trunk mechanical proper-ties and other pain psychology models (acceptance and commit-ment, misdirected problem solving, self-efficacy, and stress-diathesis) [35] and their accompanying psychological processes(i.e., cognitive flexibility in beliefs, attempts to solve problem,beliefs about the controllability of pain and coping skills, stress andanxiety) were not investigated. Likewise, other important psycho-logical processes (i.e., attention and emotion regulation, distortion,expectations, helplessness, locus of control, stop rules, overtbehaviour) and social-cultural-religious-environmental factors(i.e., spouse/co-worker/supervisor/spiritual support, job control,effort-reward imbalance, over-commitment) were not addressedand are important considerations.

Trunk stiffness and damping are one aspect of motor control,and other measurable dimensions, such as movement variabilityand movement-based subgroups could provide further contextregarding the participant heterogeneity. The motor control taskinvolved in this study is a measure of the participant’s automatic

postural response and requires only slight forward or backwardtrunk movements, which may not reflect more planned andfunctional movement tasks that could potentially be more ‘fearinducing’ to the participant (i.e., forward bending, rotation oftrunk or lifting). There has been a recent call in the literature toprioritize research aimed at providing a better understanding ofthe mechanisms by which yellow flags can affect the developmentof persistent pain and disability [36]. Physiology based studies,which examine both the motor control and psychological systemsare ideally suited to serve this role and are part of ongoingresearch.

ConclusionThe data suggest fear of movement (as measured by the TSK)

relates, at least weakly, to trunk mechanical properties, which areconsidered to be an important component of the biologicalpresentation of people with LBP. These findings lend furthersupport to the necessity to recognise the interaction betweenbiomechanical and psychological aspects of LBP rather than theirconsideration in isolation. It is possible that other psychosocialdimensions or pain psychology models may be related tobiomechanical features (i.e., trunk mechanical properties, muscleactivity, and movement patterns) in specific subgroups of LBP.Further integration of other potentially modifiable systems and

Table 4. Regression analysis (r2, P-value) between mechanical properties and psychosocial measures.

Forward stiffness Backward stiffness Forward damping Backward damping

r2 P-value r2 P-value r2 P-value r2 P-value

TSK 0.33 0.03* 0.22 0.09 0.02 0.60 0.24 0.07

PHODA-SeV 0.04 0.47 0.01 0.75 0.11 0.26 0.00 0.84

FABQ – W 0.18 0.12 0.01 0.69 0.01 0.69 0.12 0.22

FABQ – PA 0.21 0.12 0.04 0.50 0.05 0.47 0.03 0.60

PCS 0.21 0.10 0.01 0.77 0.02 0.66 0.10 0.23

CES – D 0.02 0.62 0.00 0.87 0.20 0.11 0.03 0.59

QBPDS 0.05 0.46 0.01 0.82 0.07 0.35 0.00 0.97

NPRS 0.00 0.99 0.01 0.82 0.07 0.36 0.00 0.33

Age 0.00 1.00 0.09 0.29 0.05 0.44 0.10 0.26

*- P,0.05.Stiffness (K) = (N/m), Damping (B) = (N s/m), TSK = Tampa Scale for Kinesiophobia, PHODA-SeV = Photographs of Daily Activities Short electronic Version, FABQ - W = FearAvoidance Beliefs Questionnaire - Work subscale, PCS = Pain Catastrophizing Scale, CES-D = Center for Epidemiological Studies – Depression scale, QBPDS = Quebec BackPain Disability Scale, NPRS = Numeric Pain Rating Scale.doi:10.1371/journal.pone.0067779.t004

Table 5. P-values (independent t-tests) for comparison of mechanical properties between groups stratified by median value ofpsychosocial variables.

Forward stiffness Backward stiffness Forward damping Backward damping

High TSK (.38) 0.03* 0.15 0.57 0.15

High FABQ-W (.12) 0.01* 0.49 0.29 0.49

High FABQ-PA (.11.5) 0.06 0.21 0.80 0.21

High PCS (.13) 0.22 0.84 0.65 0.84

High PHODA-SeV (.38.7) 0.22 0.72 0.21 0.72

* = P,0.05.Stiffness (K) = (N/m), Damping (B) = (N s/m). TSK = Tampa Scale for Kinesiophobia, FABQ-W & PA = Fear Avoidance Beliefs Questionnaire-Work & Physical Activitysubscales, PCS = Pain Catastrophizing Scale, PHODA-SeV = Photographs of Daily Activity – Short electronic Version.doi:10.1371/journal.pone.0067779.t005



more thorough investigation of the components within variouspain psychology models hold promise in provision of a broaderunderstanding of this multidimensional disorder.


Provided substantial contribution to conception and design: NVK RJEMSPWH. Involved with data collection and analysis: NVK WvdH. Involved

with data collection and analysis: NVK WvdH. Involved with interpre-tation of data: NVK RJEMS WvdH PWH. Provided funding: PWH.Drafted the article: NVK. Revised the manuscript critically for importantintellectual content: NVK RJEMS PWH. Provided final approval of theversion to be published: NVK RJEMS WvdH PWH.

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Altered Postural Sway and Fear of Fall in Patients Suffering from Non-specificLow Back PainSadhana Verma1*and Ajay Bharti2

1Physiotherapy Department of Saaii College of Medical Science and Technology, Kanpur, UP, India2Physiotherapy Department of Saaii College of Medical Science and Technology, Kanpur, UP, India*Corresponding author: Sadhana Verma, Assistant Professor, Physiotherapy Department of Saaii College of Medical Science and Technology, Kanpur, India, Tel:+919599961160; E-mail: [email protected]

Received date: March 21, 2017; Accepted date: April 21, 2017; Published date: April 28, 2017

Copyright: © 2017 Verma S, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricteduse, distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

Objective: The purpose of this study is to determine whether balance response of low back pain patients isdifferent from healthy controls under various up right standing conditions, and also to find out whether body sway isrelated to the fear of fall in low back pain individuals.

Method: A sample of 130 subjects was taken in the study through convenient sampling. The postural sway of thesubjects was analyzed by using a Sway meter and Fear of Fall was calculated by using a Fall Efficacy Scale.

Result: The results show that greater sway occurs in the patients suffering with Low Back Pain than compared tohealthy control group, and FES value and TSOFEC value are correlated to each other (r value=0.23).

Conclusion: Thus the study concludes that patients with low back pain exhibit greater postural sway than healthycontrols and the decreased postural stability in people with low back pain is correlated with fear of fall when extrastress has been laid on the balancing system.

Keywords:

IntroductionHuman postural balance relies on information from somatosensory,

vestibular and visual systems. Postural stability depends also on theefficiency of the motor function: joint stability and muscle activity. Theperformance of the postural balance system is affected by age,neurological dysfunctions, cerebro cranial injuries, and motor organdiseases [1].

A vital role in maintaining balance is played by the spine.Dysfunctions of the spine influence on control of posture in uprightposition. Lower back pain is a significant social problem. Low backpain is usually defined as pain, muscle tension or stiffness localizedbelow the costal margin and above the inferior gluteal folds, with orwithout leg pain (sciatica) [2].

Low back pain (LBP) is a substantial health problem. It affects up to80% of the adult population and accounts for considerable healthcareand socioeconomic costs [3].

The most used classification for pain in the lumbar spine byclinicians is specific or nonspecific LBP. A specific low back paindiagnosis (about 1-2% of all patients with early low back pain) isattributed to Low back pain, referring to any diagnosis from a systemicdisease, infection, injury, trauma, cauda equine or structural deformity.Nerve root pain usually represents about 5% of the pain in patientswith a disc prolapses and spinal stenosis [4].

Approximately 90% cases of back pain have no identifiable causeand are designated as Nonspecific. Non-specific low back pain means

that the pain is not due to any specific or underlying disease that canbe found. It indicates the structure problem of spine. It is thought thatin some cases the cause may be a sprain (an over-stretch) of a ligamentor muscle [5]. And other common cause like unaccustomed activities,poor posture, muscular, strain, obesity arthritis of spine andoccupational cause [6].

Low back pain can be acute sub-acute or chronic patients with acutelow back pain is usually defined as the duration of an episode of lowback pain persisting for the less than 6 week; sub-acute low back painas low back pain persisting between 6 to 12 week; chronic low backpain persisting for 12 week or more [5].

Posture sway in quite standing is often studied as a measure ofposture control. Many instrument ranging from the simple once likelord’s sway to the more sophisticated instrumentation, post urography,utilizes force plate to measure Ground Reaction Force, are used tomeasure the postural sway [7].

The purpose of this study is to determine whether balance responseof low back pain patients is different from healthy controls undervarious up right standing conditions. It is also determined in thepresent study whether body sway is related to the fear of fall in lowback pain individuals.

MethodologyA collective sample of 130 human subjects between age group 40-73

years, was selected by convenient sampling. The subjects were recruitedfrom the orthopedics department of LLR Hospital Kanpur. Anapproval by the Institutional Review Board was granted and aninformed consent was obtained from each subject.

Journal of Novel Physiotherapies Verma and Bharti, J Nov Physiother 2017, 7:3DOI: 10.4172/2165-7025.1000347

Research Article OMICS International

J Nov Physiother, an open access journalISSN:2165-7025

Volume 7 • Issue 3 • 1000347

Inclusion criteria

• Person with nonspecific low back pain for at least 6 weeks age40-73 year.

• Participants should have at least 1 episode of low back pain prior tostudy [8].

• Normal lower extremity in neurological examination.• Low back pain more severe than leg pain [9].• Faller and non-faller low back pain patients are included in the

study [10].• Both male and female patients participated in study [10].

Exclusion criteria

• More prominent radicular leg pain.• Previous spinal surgical application.• Pregnant ladies are excluded.• Patients with herniated disc (PIVD) [9].• Specific spinal pathology (e.g. malignancy inflammatory joint,

infection) [8].

Protocol

This is an experimental study performed in LLR hospital Kanpur. Asample of 130 subjects (100 in LBP Group and 30 in healthy ControlGroup) was taken in the study. The participants were selected on basisof exclusion and inclusion criteria. A signed consent was obtainedfrom each participant then procedure was fully explained to thepatients.

Procedure

The participants were explained about the need of the study. Thenthe details required for responding to the scale were given to thesubjects. One data collection session included two tests.

• Sway determination by using a sway meter• Fear of fall determination by using a FES (fall efficacy scale) scale.• Sway was calculated in our study by using a sway meter and in this

one data collection session included tasks which were performed 3times to test for reliability. The participants stood barefoot on thefloor as well as on the foam with their feet no more than 3 inchesapart while the Fear of fall was calculated by using on FES Scaleconsisting of 10 questionnaires.

Sway

130 subjects participated in the study, among which 100participants belonged to the LBP group, while 30 participants belongedto the healthy control group. In this study postural sway in standingwas analyzed with sway meter for both the groups. Sway meter wassnugly fit at the ASIS sway meter was placed posterior to subject.Subjects were asked to stand on floor as well as on foam, maintaining adistance of 3 inches between the feet. A graph sheet was placed behindthe subject. Graph sheet was leveled in such a way that the rod of swaymeter was maintained in horizontal position when starting themeasurement graph sheet was secured to prevent displacement duringmeasurement. Subjects were instructed to keep their hands by theirsides and stand in erect position. Starting point is marked in graphsheet before taking sway. Each trial was 30 sec subject was given restperiod after each trial. Total four tasks were performed by the

participants by challenging either the proprioception or the visualsystem as shown in Table 1.

S.no. Visual Proprioception

1 Eyes open Stable support

2 Eyes closed Stable support

3 Eyes open Foam

4 Eyes closed Foam

Table 1: Four tasks combination with challenged visual andproprioception system.

Then for each task 3 trials were taken. Total 12 trials were takenamong which, 6 trials on foam with eyes open and eyes closed and sixtrials on floor with eyes open and eyes closed. After taking the sway,the small boxes in graph sheet were being counted, in vertical lengthand horizontal length.

Fall efficacy scale

The participants were explained about the aim of study. The scaleknown as FES (Fall Efficacy Scale) was used for the assessmentprocedure. In this patients were asked 10 questions, in which, onequoted as very confident, whereas ten as not confident at all. A totalscore of greater than 70 indicated that the person had a fear of fallingwhile a score less than 70 showed the person had no fear of fall.

Data AnalysisThe data was managed on excel sheet and was analyzed using SPSS

(Statistical package for social sciences) software version 17.0. In orderto analyze the sway alteration between the experimental group and thecontrol group “t Test” was used while a “Pearson Correlation Test” wasperformed to find out the relation between sway and Fear of Fall.Descriptive statistics and correlation values were calculated betweenvarious variables for all statistical tests the level of significance set as P≤ 0.01 and P ≤ 0.05.

ResultThe result was evaluated on the basis of the readings obtained

through the scales. The minimum age of the subjects was taken as 40 ±9.55 years and the maximum age was 73 ± 9.55 years (Table 2).

Minimum Maximum S.D

Age 40 73 9.55

Table 2: Basic characteristic of low back pain patients.

The mean of total sway on foam with eyes open for the controlgroup is calculated as 573.65 and the standard deviation as 300.49. Themean of total sway on foam with eyes open for the experimental groupis 837.02 while the standard deviation as 632.66. This shows that thesway is more significant in the experimental group (Graph 1, Table 3).

Citation: Verma S, Bharti A (2017) Altered Postural Sway and Fear of Fall in Patients Suffering from Non-specific Low Back Pain. J NovPhysiother 7: 347. doi:10.4172/2165-7025.1000347

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Graph 1: Total sway on foam with eyes open in control group andexperimental group.

SWAY

Mean SD

Control Experimental Control Experimental

TSOFOE 575.65 837.02 300.49 632.66

TSOFCE 849.27 1163.9 552.14 765.47

TSOGOE 292.86 529.28 152.99 442.26

TSOGCE 360.74 442.54 194.11 479.03

TSOFOE=Total sway on foam with eyes open

TSOFCE=Total sway on foam with eyes closed

TSOGOE=Total sway on ground with eyes open

TSOGEC=Total sway on ground with eyes closed

S.D=Standard deviation

Table 3: Total sway in low back pain group and control group.

The mean value of total sway on foam with eyes closed for thecontrol group is calculated as 849.27 and the standard deviation as552.14. The mean of total sway on foam with eyes closed for theexperimental group is calculated as 1163.90 and standard deviation as765.47 (Graph 2, Table 3).

Graph 2: Total sway on foam with eyes closed in control andexperimental group.

The mean of total sway on ground with eyes open for the controlgroup is calculated as 292.86 and standard deviation as 152.99. The

mean of total sway on ground with eyes open for the experimentalgroup is calculated as 529.28 and standard deviation as 442.26 (Graph3, Table 3).

Graph 3: Total sway on ground with eyes open in control andexperimental group.

The mean of total sway on ground with eyes closed for the controlgroup is calculated as 360.74 and standard deviation as 194.11. Themean of total sway on ground with eyes closed for the experimentalgroup is calculated as 442.54 and standard deviation as 479.03 (Graph4, Table 3).

Graph 4: Total sway on ground with eyes closed in control andexperimental group.

The t value for the total sway on foam with eyes open is obtained as2.18 while the P value as 0.05, which is a significant value and thisshows that the sway is more significant in the low back pain groupthan the control group when the level of significance is 0.05.

The t value for the total sway on foam with eyes closed is obtained as2.09 while the P value as 0.02 this show that the sway is moresignificant in low back pain group than control group when the level ofsignificance is 0.05.

The t value for the total sway on ground with eyes open is obtainedas 2.87 while the P value as 0.003 this show that sway is significant inlow back pain group than control group when the level of significanceis 0.01.

The t value for the total sway on ground with eyes closed is obtainedas 0.91 while the P value as 0.02 this shows that sway is significant inlow back pain group than control group when the level of significanceis 0.05 (Table 4).


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Sway T value P value

TSOFEO 2.18 0.05**S

TSOFEC 2.09 0.02**S

TSOGOE 2.87 0.003*S

TSOGEC 0.91 0.02**S

*Level of significance 0.01** Level of significance 0.05

TSOFOE= Total sway on foam with eyes open

TSOFCE=Total sway on foam with eyes closed



S=significance

Table 4: Total sway in low back pain group and control group.

The r value for the Correlation between FES and total sway on foamwith eyes open is 0.11 while the P value is 0.25 which is not significant(when the level of significance is 0.05). Hence shows that FES valueand TSOFOE value are not correlated to each other.

The r value for the correlation between FES and total sway on foamwith eyes closed is 0.23 while the P value 0.02 which is a significantvalue (when the level of significance is 0.05). Hence shows that FESvalue and TSOFEC value are correlated to each other.

The r value for the Correlation between FES and total sway onground with eyes open is 0.14 while the P value is 0.17 which is notsignificant (when the level of significance is 0.05). Hence shows thatFES value and TSOGOE value are not correlated to each other.

The r value for the Correlation between FES and total sway onground with eyes closed is 0.13 while the P value is 0.21 which is notsignificant (when the level of significance is 0.05). Hence shows thatFES value and TSOGEC value are not correlated to each other (Table5).

TSOFEO TSOFEC TSOGEO TSOGEC

FES

p value r value p value r value p value r value p value r value

0.25 0.11 0.02** 0.23 0.17 0.14 0.21 0.13

NS S NS NS

TSOFOE=Total sway on foam with eyes open

TSOFCE= Total sway on foam with eyes closed



FES= Fall efficacy scale

S=Significance and NS=Not significance

*Level of significance 0.01 ** Level of significance 0.05

Table 5: Correlation with total sway and FES.

DiscussionThe purpose of this study is to find the difference in sway in case of

LBP group and control group (consisting of healthy subjects) as well asto find the relation between the postural sway and fear of fall in lowback pain individuals. During standing an individual normally exhibitssmall range postural shifts or postural sway cycling intermittently fromside to side and from heel to toe. In normal individuals the AP sway isapproximately 12 degrees [11].

But this sway may vary in different situation as we found in ourstudy the sway was increased in the LBP group as compared to thesway in the control group which consisted of the healthy individuals.The result showed a significant difference between the sway in the LBPgroup and the control group [12]. The altered sway pattern in both thegroups may underline the role of “Pain Inhibition” in the observedpostural response [13].

The sway was examined under four conditions on floor with eyesclosed and on the foam with eyes open as well as with eyes closed in

order to alter the visual proprioception and joint proprioception so asto challenge the balance system of our body. It is noted that visualdeprivation caused an increase in postural sway in both the groups[1,14].

Also the results showed a positive correlation between the perceivedfear of fall and sway in LBP individuals. This correlation has beenfound positive only in the case when the persons with LBP werestanding on ‘Foam’ with eyes closed. The proposed reason may bewhen the complexity of the task increased the postural stabilitydecreased in persons with LBP [15].

During standing on foam the CNS of the healthy personsignificantly up weighted the proprioceptive signals from theParaspinal muscles and down weighted those from ankle muscles tocontrol postural balance. As standing on foam is less reliableproprioceptive input from the ankle joint. Therefore the CNS shouldrely more on the proprioceptive input from other joints such aslumbosacral region to keep the postural balance. These findings


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suggest strongly that the persons with recurrent LBP have alteredpostural control. Moreover, the CNS of the persons with LBP seemedto select the same postural control strategy (i.e. proprioceptive controlat the ankles) as in normal bipedal standing on stable support surface,showing a decrease in postural control variability. This posturalstrategy leads to less stable postures when postures when posturaldemands increase and also may generate a fear of falling in theindividuals [15,16].

Another reason for the positive correlation between fear of fall andsway may be fear avoidance model according to which pain relatedfear leads to the avoidance or escape from activity which further leadsto disability and inability to maintain balance [17-19].

Thus our study aims to correlate the fear of fall and sway in LBPindividuals so that in future attempts can be made through thetreatment protocol to decrease or avoid these difficulties.

Strength and limitations

The strength of the current work is that it may be that only studywhich used a sway meter to measure sway discriminated between LBPgroup and non-low back pain group. The control of standing balance isa task of maintaining the body COM within the limits of BOS achievedby providing force on the support surface excursion of the COP thepoint of application of the ground reaction force measured by a forceplate has been widely used to represented postural sway as an index ofbalance control. However these measures involve technical devices thatcan be usually and require processing protocols that can make themunfeasible for many clinics and research facilities. The need for asimple measure of postural sway exits due to the issue of balanceproblem and risk of fall. So this low technical sway meter was designedto address the need of clinicians and researchers with limitedresources. It involves no electronics or computer processing. Thusassessment can be conducted in variety community setting and healthcare facilities.

The study also has a few limitations.

• First limitation is linked to the absence of cognitive status ofparticipants.

• A final limitation is the inability to measure the alteration in swaywith the orientation of the vestibular system.

• The limitation with respect to the sway include the fact thatdynamic sway was not evaluated

• Absence of random sampling.

Future research

Future study should focus on the development of new experimentalprotocols based for example on 3D analysis to clearly verify thecorrelation between fear of fall and sway. These studies should evaluatethe importance of the correlation for its influence on each anatomicalsegment of the body.

ConclusionPatients with low back pain exhibit grater postural sway than

healthy controls. Further the decreased postural stability in people withlow back pain is correlated with fear of fall as extra stress has been laidon the balancing system.

AcknowledgementWords are medium of expression, if properly communicated and

comprehended. Nevertheless sentiments do remain inexplicable.Words can ever explain my feeling of gratitude indebtness andreverence for my esteem guide as well as friend Dr Garima Gupta (PT),who has been constant source of inspiration, during my dissertationwork. Her thoughtful suggestion, valuable criticism and enthusiasticattitude were much valuable for this project.

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Karimi and Saeidi, J Spine 2013, 2:4DOI: 10.4172/2165-7939.1000139

Review Article Open Access

Volume 2 • Issue 4 • 1000139J Spine, an open access journalISSN: 2165-7939

A Review of Relationship between Fear Avoidance Beliefs and Postural Stability in Non Specific Chronic Low Back PainAbdolkarim Karimi1 and Marzieh Saeidi2*1Assistant Professor, School of Rehabilitation, Isfahan University of Medical Sciences, Iran 2Physiotherapist of Shariati Hospital, Management Treatment of Isfahan social security organization, Iran

AbstractIntroduction: Low back pain (LBP) is one of the most prevalent diseases in most developed and developing

countries, affecting 70% to 80% of adults at some time during their lives. Recent evidence suggests that psychosocial

factors especially fear-avoidance beliefs (FAB) are important in predicting patients who will progress from an acute

to a chronic stage as well as failure of interventions. The aim of this study is to review the Relationship between Fear

Avoidance Beliefs and Postural stability in non specific Chronic Low Back Pain (CLBP).

Methods: In this narrative article we have searched PubMed, CINHAL, APTA and MEDLINE data bases. The key words included: chronic low back pain, fear avoidance beliefs, posture, stability, balance, motor control, center of

pressure and force plate. The inclusion criteria were being related to FAB and postural stability and adults with non

specific CLBP, in English language, up to 2013, regardless of their study design.

Results: The results showed that psychological factors such as FAB influence the chronicity of LBP, a group of studies indicated that FAB is related to pain and disability. Another group of studies indicated that postural stability is

related to pain and disability. The only study on the relationship between postural stability and FAB did not found any

significant relationship.

Conclusion: FAB is related to pain and disability. Postural stability is related to pain and disability. More studies

with stronger methodology such as larger population with control group are needed for evaluating the relationship of

FAB and postural control.

*Corresponding author: Marzieh Saeidi, Physiotherapist of Shariati Hospital, Management Treatment of Isfahan Social Security Organization, Iran, E-mail: [email protected]

Received April 30, 2013; Accepted July 08, 2013; Published July 10, 2013

Citation: Karimi A, Saeidi M (2013) A Review of Relationship between Fear Avoidance Beliefs and Postural Stability in Non Specific Chronic Low Back Pain. J

Spine 2: 139. doi:10.4172/2165-7939.1000139

Copyright: © 2013 Karimi A, et al. This is an open-access article distributed under

the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and

source are credited.

Keywords: Chronic low back pain; Fear avoidance beliefs; Stability;Motor control

IntroductionLow back pain (LBP) is one of the most common health problems

which affect 60% to 80% of adults at some time during their lives [1,2]. About 85% of patients with back pain are classified as non specific chronic low back pain [3]. Although most of the time, LBP is a self-limiting disorder and a majority of these patients will improve rapidly [4], half of them has a long history of multiple episodes [5] and in a small group of them (about10%), pain will become chronic [6-8]. This group of patients allocate about 80% of costs to themselves [9]. Consequently, LBP is a major public health problem with an immense socioeconomic burden in most developed and developing countries.

Studies on patients with acute or sub acute LBP reveal several factors influence on progression to chronicity of LBP such as: high level of psychological distress, dissatisfaction with employment, longer duration of symptoms, previous history of LBP, radiating pain and higher initial disability level [10-13], psychosocial factors like the patients attitudes and beliefs, pain and movement related fear, stress, depression, job satisfaction, self confidence and self assurance are very important in CLBP [14,15]. The cognitive-behavior concept of developing chronic pain is appearing as fear-avoidance behavior at early stage. Cox et al. explained in a model the reason of pain exaggeration and the reason of developing pain in to chronic stage in some of the patients while improving in others [16]. According to this model, the patient’s fear of pain, and subsequent avoidance behavior, are determined by the relation between sensory and emotional components of pain. The hypothesis is that the patients believes and fears concerning symptoms and activity lead to unhelpful ways of managing symptoms, including avoidance behaviors, decreasing activities of daily living, job and recreation which reflect a state of not feeling well. Also failing to diagnose factors which influence their condition can lead to use an inappropriate treatment approach.

In individuals with LBP, the Fear-Avoidance Belief Questionnaire (FABQ) quantifies pain-related fears and believes about the necessity of changing the behavior of pain avoidance [17]. Pain related fear refers to a condition in which the patient has an excessive, irrational, and debilitating fear of physical movement and activity, resulting in feelings of vulnerability to painful injury or re-injury [18,19]. Biomechanical factors such as strength or endurance, flexibility spinal stability and neurophysiologic factors have been studied in several investigations [20-22]. It is important for physicians and physiotherapists to have enough information in this area in order to be able to recognize the obstacles of the patients’ improvement and adopt an appropriate strategy accordingly.

Optimal postural control is an essential requirement to perform daily activities. Postural stability is a component of postural balance which indicates the ability of maintaining a certain posture and is described by center of pressure (COP) excursion [23,24]. Many factors may contribute to control postural stability including age, neurological or musculoskeletal disorders such as LBP and biomechanical factors such as muscle endurance [21,25]. The influence of LBP on postural balance is complex and affected by co-existing factors: pain, fear of pain, positive neurologic findings, adoption of an alternate movement strategy, and low muscular conditioning [24,26-30]. Several studies

Journal of SpineJo

urnal of Spine

ISSN: 2165-7939

Citation: Karimi A, Saeidi M (2013) A Review of Relationship between Fear Avoidance Beliefs and Postural Stability in Non Specific Chronic Low Back Pain. J Spine 2: 139. doi:10.4172/2165-7939.1000139

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studies on relationship between pain, disability and FAB, studies on the relationship between pain, disability and postural stability and studies on relationship between FAB and postural stability.

Pain, disability and fear avoidance beliefsPsychological factors may be related to the onset, development,

and treatment outcome of spinal pain. Strong evidence also shows that psychosocial variables generally influence more than biomedical or biomechanical factors on chronic back pain [37-43]. Recent evidence suggests that psychosocial factors are important in predicting patients who will progress from an acute to a chronic stage as well as failure of interventions [13,14]. Patients with chronic pain often demonstrate anxiety and depression [15].

Several studies have shown the relationship between pain, FAB and disability in patients with CLBP [38-43]. With regard to psychosocial factors, a growing body of published data has provided evidence that elevated pain-related fear predicted disability in patients with acute and chronic LBP [35,41-43]. People who experience pain-related fear will avoid activities they associate with increased risk for pain or (re)injury [18,19]. Therfore pain-related fear have a negative impact on the results of performance testing [35,44]. Correlation analysis in a study by Guclu indicated a significant but positive weak association between the severity of pain and fear avoidance (physical, work and overall) [45].

The relation between pain, pain related fear and functional performance is weak or non-existent in patients with CLBP [46]. A hospital case-control study in Iran, compared the psychological features in patients with low-back pain. Patients’ levels of depression and anxiety were related to occupational background. Longer duration of illness was also accompanied by higher levels of anxiety and depression [33]. Another study indicated that Pain was positively related with fear-avoidance beliefs, catastrophizing, and anxiety. In addition, job had a moderating effect on the relationship between pain and anxiety so that job indicated 24.6% of pain variance [47]. Two review articles by Leeuw [48] and Akhbari [49] indicated that there is a positive relationship between

have shown that patients with CLBP have some problems for postural control [31,32]. Fear-avoidance believes have been hypothesized as the most important psychosocial factor in predicting disability and work time loss among patients with chronic low back pain (CLBP). So identifying potentially modifiable determinants of disability in patients with LBP provides an opportunity to expand strategies of controlling socioeconomic problems. Many studies have assessed the relationship of either impairment or psychosocial factors with disability and pain [33-36], but to our knowledge, relationship between the level of Fear-Avoidance Belief (FAB) and the parameters of postural stability is not well studied and it needs more studies. The aim of this study is reviewing the studies on the relationship between psychosocial factors especially pain related fear with postural stability in non specific chronic low back pain.

MethodsIn this narrative review article the PubMed, CINHAL, APTA

and MEDLINE data bases were searched for articles on relationship between pain and pain related fear and postural stability. The related key words included: back pain, chronic low back pain, fear avoidance beliefs, postural stability, postural control, force plate and center of pressure. The criteria for evaluation of the articles were included: their title being related to the topic (defining the relationship between pain related fear, pain, disability, postural stability and postural control), with any design, up to 2013 published in English. Twenty five articles had the inclusion criteria. The studied out comes included activity and reaction time of trunk muscles, center of pressure excursion (sway), fear avoidance beliefs, pain and disability. Studies which did not evaluate the relation of these outcomes were excluded.

ResultsAccording to the inclusion and exclusion criteria 25 articles were

found which met the inclusion and exclusion criteria. These studies were summarized in Table 1 and 2. The studies were divided in 3 categories:

Table 1: Studies on Postural control, pain and disability.

Author Study design Topic ResultsLafond et al. [32] Case-control Postural balance during prolong

standing in low back pain patients

Decreasing of Cop velocity, frequency and excursion

Della Volpe et al. [58] Case-control Postural control during dynamic

standing in low back pain patients

Increasing of Cop excursion

Luoto et al. [33] RCT, n=99(LBP), n=61(Healthy)

Reaction time and COP velocity Postural control was weaker in CLBP and improved after rehabilitation

Mann et al. [24] Case-control Postural control in CLBP Cop velocity was higher in CLBP

Brumagne et al. [26] Case-control, n=52(LBP), n=33(Healthy)

Postural control in CLBP Cop excursion was higher in CLBP

Brumagne et al.

[54]Case-control, n=21(LBP),

n=24(Healthy)Postural stability and postural control

strategy in persons with recurrent LBP

persons with recurrent LBP use the same postural control

strategy even in standing on an unstable support surface

Ruhe et al. [27] Systematic review Postural control in CLBP Cop velocity and excursion were related to LBP but not pain intensity

Ruhe et al. [60] Case-control, n=77(LBP), n=77(Healthy)

Is there a relationship between pain

intensity and

postural sway in patients with CLBP

COP mean velocity and sway area are closely related to self-reported pain scores.

Ruhe et al. [61] Case-control, n=38 (LBP), n=38(Healthy)

Pain relief is associated with

decreasing postural

sway in patients with CLBP

Alterations in pain intensities are closely related to changes in

postural sway.

Takala and Juntura [28] Cohort, two year follow up, n=430 Role of functional tests in prediction

of LBP

Weak performance was related to low stability and endurance

Moseley et al. [30] Comparative before and after, n=16 Relationship between experimental pain and Postural control in CLBP

Pain causes delay in postural muscle activation

Mazaheri et al. [57] systematic review postural sway during quiet standing in LBP

Most studies reported an increased postural sway in LBP or no

effect of LBP on postural sway.


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pain-related fear, pain intensity and disability; in addition, pain-related fear results in poor clinical outcomes.

Pain, disability and postural stabilitySeveral studies have shown that postural control parameters

change in CLBP however, there is controversy on relationship between pain and postural control parameters, [32,37,50-56] so that some of them indicated increasing postural sway [53], others have shown decreasing postural sway [51] while in the other studies, there was not any significant relationship between pain intensity and postural sway [54]. Of course one of the two recent systematic review article has revealed that pain results in enhancement of cop excursion [27]

while the other systematic review indicated that there is equal number of studies showing increased sway in LBP, or no effect of LBP on sway [57].

In LBP patients, delayed contraction of trunk muscles, which results in reduced stiffness of the spine at the time of initiation of the movement, occurs when the equilibrium of the spine is disturbed by rapid movements of the upper or lower limbs [51,52]. In recent years, it has become evident that muscle pain can interfere with motor control strategies and different patterns of interaction are seen during rest, static contractions, and dynamic conditions [51].

Altered postural adjustments of the trunk muscles during pain are not caused by pain interference but are likely to reflect development and adoption of an alternate postural adjustment strategy [30]. Although postural activation of the deep trunk muscles is not affected when central nervous system resources are limited, it is delayed when the individual is also under stress [57,58].

In CLBP patients, postural stability under challenging conditions such as prolonged standing is maintained by an increased sway in anterior-posterior direction. This alteration in postural strategy may provide a dysfunction of the peripheral proprioceptive system or the central integration of proprioceptive information [59]. These findings point to possible neurophysiologic mechanisms that could help explaining why fear of pain is a strong predictor of pain-related disability [60] (Table 2).

Another study in 2011 has shown postural stability is related to higher level of pain intensity and lower level of pain intensity don’t due to alteration of postural stability [61]. A new study showed that disability is related to duration of LBP, higher level of pain intensity, FAB and stability (velocity in the forward direction) [62].

Studies on relationship between FAB and postural stabilityThe only study of concurrent and predictive validity of postural

balance in LBP patients did not found any significant relationship between fear avoidance beliefs and postural stability (COP excursion and velocity) [50]. Baseline and 12-week follow-up results of 97 LBP patients were evaluated. The correlations between CoP measurements and pain, fear of pain, and physical function were poor. There were no significant differences in CoP measurements between patients with no change or deterioration and patients with improvement in pain and back-specific function [50]. Also another study has evaluated the relationship between kinesiophobia and trunk muscles function but they were not related significantly [32]. Correlation analysis in a study by Kusters showed that neither fear of movement and catastrophizing nor pain was related to either reaction time (RT) or movement time (MT) [63]. Another study by Afshar-nezhad also indicated that fear

Table 2: Studies on pain and fear of pain and disability and postural control.

Author Study design Topic ResultsCrombez et al. [41] Cross sectional,n=124 Relationship between pain and fear of pain

with disability in CLBPPain is related to FAB and disability

Klenerman et al. [42] Cohort, one year follow up, Role of fear avoidance beliefs in prediction

of LBP

7% become chronic (66% due to fear of pain)

Afshar Neghad et al. [64] Cross sectional n=50 Relation between fear of movement, pain

and disability in chronic low back pain

fear of movement, pain intensity and age are

related to disability

Akhbari et al. [49] review The Fear of Movement/Pain inMusculoskeletal Pain-A Review

fear of pain can be as disabling as pain itself

Gatchel et al. [14] Cohort, one year follow up, n=221 Role of psychological factors in CLBP High prevalence of psychological diseases in CLBP

Linton [15] Systematic review Role of psychological factors in CLBP and neck pain

clear link between psychological variables and

neck and back pain onset

Sajjadian et al. [47] Cross sectional n=50 fear-avoidance believes, pain

catastrophizing and anxiety effects on chronic low back pain in women

Chronic low back pain can be predicted by fear-avoidance beliefs and catastrophizing

Guclu et al. [45] Cross sectional n=105 The Relationship Between Disability, Quality of Life

and Fear-Avoidance Beliefs in CLBP

Higher levels of anxiety, depression, FABQ (work) leads to higher level of disability

Ramond et al. [38] systematic review Psychosocial risk factors for chronic low

back pain in

primary care

Depression,psychological distress, passive coping

strategies and FAB were independently linked

with poor outcome

Leeuw et al. [47] Review Paper The Fear-Avoidance Model of

Musculoskeletal Pain: Current State of Scientific Evidence

pain-related fear is associated with catastrophic

interpretations of pain, avoidance behaviors,

pain intensity and disability

Davis et al. [62] Cross sectional n=235 Variables Associated With Level of Disability

Disability is related to duration of LBP, higher level of pain intensity and FAB, and stability

(velocity in the forward direction

Maribo et al. [43] Validity, n=97 Postural balance in low back pain patients No relationship between pain, FAB and COP excursion

Lamoth et al. [32] Case-control Relationship between pain and fear of pain

with muscle coordination in CLBPPain intensity, kinsiophobia and disability were

not related to postural muscle function but were

due to LBP


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of movement; pain intensity and age are related to disability [64]. Guclu showed that when fear-avoidance (physical, work and overal), increased, disability increased as well [45]. In the study of Crombez et al. [65] a moderately significant relation was found between physical and work fear-avoidance behavior and disability.

DiscussionThe aim of this study was to review the relationship between

psychological factors focusing on FAB, pain, disability and postural stability.

According to the results, first group of studies showed that psychological factors such as FAB influence the chronicity of LBP; in addition FAB is related to pain and disability.

Another group indicated that postural stability is related to pain and disability. Also a few studies indicated that FAB is related to postural stability in subjects without CLBP but only one study has investigated this relationship in patients with CLBP in which there was not seen any significant relationship between FAB and postural stability.

Sajjadian et al. showed that Pain was positively related to fear-avoidance beliefs, catastrophizing, and anxiety [47]. In her study, fear-avoidance beliefs and catastrophizing explained 45.6% of the variance of the pain. In addition, she revealed that job had a moderating effect on the relationship between anxiety and pain. Her study carried out on women who reported higher level of FAB compared to men [47]. Sions and Hicks [66] explained the lack of a significant relation between fear avoidance and disability in their Hispanic patients, in these patients. It seems that pain intensity and ethnic characteristics are underlying factor for this controversy. Hicks et al stated that fear and avoidance behavior in work is a highly specific finding for disability [67]. George et al. [68] demonstrated that in patients with chronic low back pain, the single predictor of disability was fear avoidance behavior (work). As to the study of Waddell et al. [17], severity of pain and fear avoidance behavior was found to be predictors of disability [17]. The relationship between pain related fear and performance appeared stronger in studies where patients were observed under strictly controlled conditions, and weaker in studies where patients were observed in a less controlled environment [41,69]. However the relationship between pain, fear avoidance beliefs and postural stability was different in these studies. According to the study by Isableu and Vuillerme [70] in quiet standing, postural sway will decrease because of trunk stiffening strategy or ankle strategy but during standing on foam, postural stability will decrease in patients with CLBP compared to healthy subjects; while in another study by Brumagne et al. [54], the results showed that in both quiet standing in a stable surface and unstable surface (foam) is different in patients with CLBP compared to healthy subjects. These results support the hypothesis that in more complex postural conditions postural stability decrease in persons with LBP compared to healthy controls. Ruhe et al. demonstrated a linear relationship between pain intensity and postural sway velocities in both sagital and frontal plans [60], however, the sway velocity in frontal plan increased at a faster rate. In addition, his study confirms the altered postural sway characteristics previously reported in a systematic review of NSLBP sufferers [27]. The most important finding of his study was that higher intensity of pain perception is related to COP measurements which can describe why in some studies pain intensity was not related to the postural stability. Therefore the neurological alteration previously described

[30,71-74] may only have an impact on COP measures at medium to high intensities (more than 5 in numeric rating scale of pain). These results are in agreement with observations of Lihavainen et al. [75] who conducted a similar study in a geriatric population, of course,

pain was measured based on a subdivision into mild or moderate/severe pain only in their study and the studied population was different characteristically. However, according to using a protocol based on best evidence [60], future studies are not needed to confirm these findings using the same protocol. Considering the inclusion criteria, focusing on those with higher pain intensity to reach significance compared to controls more readily, the results may also interpret the results of studies (e.g. Brumange et al. [54] and Mok et al. [29]), in which there were not significant differences in postural sway between symptomatic individuals and healthy controls because of low pain intensities of the NSLBP participants enrolled. There is evidence that higher COP sway is associated with a higher risk of falling in the elderly [76] therefore the importance of suitable pain control in elderly pain sufferers to avoid falls. Furthermore, as pain interference appears a likely underlying mechanism, the focus of a rehabilitative approach in pain sufferers with increased COP excursions should be on pain reduction rather than proprioceptive training.

As the lower back motor tasks are often considered both painful and threatening by patients, it is hard to distinguish whether performance insufficiency is attributed to pain experience or to pain related cognitions. Only a few studies tried to enable analysis of pain effect apart from cognition effect. Lamoth et al. studied the influence of both parameters (pain and fear of pain) on gait in healthy subjects [77]. Their results show that only pain influenced on gait parameters. Considering subjects awareness of disappearing pain eventually, pain-related fear may not be representative for this population since pain is present continuously and pain-related fear is much more substantial. Kasters [63] and Luoto [33] indicated slower reaction time of patients compared to healthy subjects concluded that the reaction time in CLBP patients was not influenced by cognitions. The contradiction of their studies with findings of previous studies demonstrating a deteriorating role for pain-related cognitions and reaction time performance [64,78,79] may be due to differences in experimental design (i.e. different reaction time tasks).

In sum, there is lack of knowledge concerning the relation between pain, pain-related cognitions and deviations in CLBP patients’ motor performance. As it is conceivable that managing pain demands a different treatment approach than managing pain-related cognitions, this knowledge might be useful to increase CLBP therapy effectiveness.

The only recent study of concurrent and predictive validity of postural balance in LBP patients revealed no association between COP measures and pain, fear of pain, and physical function. According to recommendations for COP measures were published in 2010 in order to reduce measurement errors, this recent study may have some errors such as being included all low back patients, not considering age groups and procedure of measuring COP (60 second sampling duration instead of 90 second and 2 trials instead of 3-5 trials) [27,61].

Also, a high level of anxiety increased postural sway in healthy individuals, with an increment of path length in the anteroposterior axis [80]. On the other hand, Lopes found a significantly reduced body sway area and mean power frequency thorough the experiment as well as a negative correlation between anticipatory anxiety and mean sway area when compared to control participants [81]. Levitan et al. also found that patients with social anxiety disorder showed a reduced sway area and a lower velocity in the mediolateral direction during presentation of all blocks of pictures compared to control [80]. His study showed that body sway in patients with social anxiety disorder is smaller than in controls independently of the presence and contents of visual information maybe because the stimulus of anxiety was not enough [80].


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To become a short story, it seems that different results of the evaluated studies are due to the way of data collection, population characteristics (physical activity and fitness level and age), inclusion/exclusion criteria, the level of pain, postural stability and fear avoidance beliefs at the beginning of the studies. Also different instruments (the questionnaires and scales for fear avoidance, pain, force plates), different procedures of measuring postural stability (quiet standing or single leg stand or sitting, with open or closed eye and the position of the hands the number of trials, frequency of filtering and capturing) and different outcome measures for postural stability (muscle activity, reaction time, COP displacement, velocity, mean frequency) used in these studies can be consider for variability of their results.

ConclusionIt can be concluded that pain related fear may be one of the factors

of failure the treatments of patients with NCLBP. FAB is related to pain and disability. Postural stability is related to pain and disability. More exact studies are needed for evaluating the relationship of FAB and postural control.

LimitationsOne of the most important limitations of this study is lack of the

statistical analysis and criterion evaluation of the included studies.

SuggestionsIt is recommended to evaluate more similar and related studies

from other data bases which focus on the topic according to their power as well as using statistical analysis of their data where it is possible. References

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RESEARCH ARTICLE

Physical activity and the mediating effect offear, depression, anxiety, and catastrophizingon pain related disability in people withchronic low back painPaul W. M. Marshall*, Siobhan Schabrun, Michael F. Knox

School of Science and Health, Western Sydney University, Penrith South, New South Wales, AUSTRALIA

* [email protected]

Abstract

Background

Chronic low back pain is a worldwide burden that is not being abated with our current knowl-

edge and treatment of the condition. The fear-avoidance model is used to explain the rela-

tionship between pain and disability in patients with chronic low back pain. However there

are gaps in empirical support for pathways proposed within this model, and no evidence

exists as to whether physical activity moderates these pathways.

Methods

This was a cross-sectional study of 218 people with chronic low back pain. Multiple media-

tion analyses were conducted to determine the role of fear, catastrophizing, depression, and

anxiety in the relationship between pain and disability. Separate analyses were performed

with physical activity as the moderator. Individuals were classified as performing regular

structured physical activity if they described on average once per week for > 30-minutes an

activity classified at least moderate intensity (� 4–6 METs), activity prescribed by an allied

health professional for their back pain, leisure time sport or recreation, or self-directed physi-

cal activity such as resistance exercise.

Results

Fear, catastrophizing, and depression significantly mediated the relationship between pain

and disability (p<0.001). However the mediating effect of catastrophizing was conditional

upon weekly physical activity. That is, the indirect effect for catastrophizing mediating the

relationship between pain and disability was only significant for individuals reporting weekly

physical activity (B = 1.31, 95% CI 0.44 to 2.23), compared to individuals reporting no

weekly physical activity (B = 0.21, 95% CI -0.50 to 0.97). Catastrophizing also mediated the

relationship between pain and fear (B = 0.37, 95% CI 0.15 to 0.62), with higher scores

explaining 53% of the total effect of pain on fear.

PLOS ONE | https://doi.org/10.1371/journal.pone.0180788 July 7, 2017 1 / 15

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OPENACCESS

Citation: Marshall PWM, Schabrun S, Knox MF(2017) Physical activity and the mediating effect offear, depression, anxiety, and catastrophizing onpain related disability in people with chronic lowback pain. PLoS ONE 12(7): e0180788. https://doi.org/10.1371/journal.pone.0180788

Editor: JianJun Yang, Southeast UniversityZhongda Hospital, CHINA

Received: July 18, 2016

Accepted: June 21, 2017

Published: July 7, 2017

Copyright: © 2017 Marshall et al. This is an openaccess article distributed under the terms of theCreative Commons Attribution License, whichpermits unrestricted use, distribution, andreproduction in any medium, provided the originalauthor and source are credited.

Data Availability Statement: All relevant data arewithin the paper and its Supporting Informationfile.

Funding: The authors received no specific fundingfor this work.

Competing interests: The authors have declaredthat no competing interests exist.

Abbreviations: FABQ-a, fear-avoidance beliefsquestionnaire – activity score; FABQ-w, fear-avoidance beliefs questionnaire – work score;










http://creativecommons.org/licenses/by/4.0/

Conclusions

These results support previous findings about the importance of fear and depression as fac-

tors that should be targeted in low back pain patients to reduce back pain related disability.

We have also extended understanding for the mediating effect of catastrophizing on back

pain related disability. Back pain patients engaged with regular physical activity may require

counselling with regards to negative pain perceptions.

Introduction

Low back pain is the musculoskeletal condition with the greatest worldwide burden of disease,defined in terms of disability adjusted life years or years lived with disability [1]. The economiccost to society is considerable, with direct annual costs of treatment in Australia estimated tobe $4.8 billion [2], and total treatment costs approximately $9 billion [3]. Despite both painand disability being associated with a range of psychosocial and physical factors [4–7], thedirect pathways that link pain and disability remain unclear. Thus clinicians and researchersare faced with difficulty designing targeted interventions to alleviate the burden of chronicback pain. One theoretical model developed to explain how pain leads to disability is the fear-avoidance model [8,9]. However, despite its popularity for explaining disability, and integra-tion into clinical trials to provide measures of treatment action, there are gaps in empiricalsupport for pathways within the fear-avoidance model.

The fear-avoidance model was originally proposed to explain how exaggerated pain percep-tion was the consequence of a heightened fear of pain and avoidance of social and physicalactivities [10]. In 2000 the model was updated to suggest that pain may lead to catastrophicthinking, with the subsequent increase in fear and physical disuse contributing to disabilityand psychological distress [9]. Recently, paths within the fear-avoidance model have beenexamined in a systematic review of mediation studies [11]. Mediation is a type of statisticalanalysis that examines proposed causal mechanisms thought to explain the relationshipbetween two variables. This review reported that fear and psychological distress, but not cata-strophizing, mediate the relationship between pain and disability. However a number of gapsin the literature were identified with regards to support for causal paths within the fear-avoid-ance model. First, studies examining the mediating effect of catastrophizing were not suffi-ciently powered based on recommended sample sizes for this type of analysis (total of 3 studiesreviewed, n = 234; range n = 64 to 103), and only one of these studies sampled from a chronicback pain population [12]. The low power, particularly for chronic back pain patients, mayexplain the disparity between the review conclusions and outcomes from intervention studiesthat suggest catastrophizing mediates the effect of various physical activity and treatment inter-ventions on back pain related disability [13]. Second, no study examined the first proposedpathway of the fear-avoidance model, which suggests that catastrophizing mediates the rela-tionship between pain and fear [9]. Finally, no information was provided about factors (e.g.physical activity, pain duration) that may moderate pathways within the fear-avoidancemodel.

In contrast to mediation, which quantifies the effect a potential explanatory variable (e.g.fear) has on the relationship between an exposure (e.g. pain) and outcome (e.g. disability),moderation is an analysis technique that examines whether an external condition influencessuch a relationship. Within the context of the fear-avoidance model and low back pain, theregular performance of a structured physical activity program (e.g. therapist guided exercise

Fear avoidance and chronic low back pain


HADS-a, Hospital Depression and Anxiety Scale –anxiety; HADS-d, Hospital Depression and AnxietyScale – depression; LBP, low back pain; METS,metabolic equivalents; ODI, Oswestry disabilityindex; PCS, pain catastrophizing scale; VAS-c,visual analog pain scale - current pain; VAS-w,visual analog pain scale - worse pain last week.


program, cardiorespiratory exercise, self-prescribed trunk exercises) is a potential moderatingvariable that has not been examined. Adherence to prescribed physical activity or exercise inlow back pain patients is typically poor, with reports of non-adherence in 50 to 70% of patients[14,15]. Moreover, physical activity levels have a negative association with disability in patientswith chronic low back pain [16]. While it is plausible to suggest that back pain patients who donot engage in regular physical activity exhibit greater fear-avoidance, thus explaining the rela-tionship between higher levels of pain and disability, this has not been well examined.

Therefore we conducted this study to provide further empirical investigation of proposedpathways within the fear-avoidance model in patients with chronic low back pain. The specificobjectives of this study were 1) to investigate whether catastrophizing, in combination withfear and psychological distress, mediated the relationship between pain and disability, 2) toinvestigate whether catastrophizing mediated the relationship between pain and fear, and 3) toexamine whether engagement with regular structured physical activity moderated the indirecteffect of catastrophizing, fear, and psychological distress on the relationship between pain anddisability.

Materials and methods

Study design

This cross-sectional study with mediation analysis used data from people with chronic lowback pain, and does not report any outcomes following specific treatment.

Participants

This study was based on data collected from 218 consecutive participants (out of 394 peoplescreened for inclusion) with chronic low back pain from the local community who attendedthe local University School of Science and Health research facility between June 2011 and July2016 (Table 1; S1 Table). Sample size estimates for mediation analysis to achieve 0.8 power[17] were based on previous data for the mediating effect of fear and depression on the rela-tionship between pain and disability (a and b pathways B = 0.40), and required a minimum of71 participants. This study was not sufficiently powered to detect significant indirect effectswhen the a and b paths (exposure to mediator, mediator to outcome respectively) were small(B = 0.14). For example a small ‘a path’ but large ‘b path’ (B = 0.60) is suggested to requiren = 365. All data collection procedures received ethical approval from the Western SydneyUniversity Human Research Ethics Committee. Written informed consent was received fromall participants prior to proceeding with data collection. Participants were eligible for the studyif they were between the ages of 18 and 65 years, had pain and/or impairment attributed to thelow back > 3-months, with symptoms reported between T12 to the gluteal folds that was notfrom a specific origin (as confirmed from previous back surgical history, spondylolisthesis, spi-nal stenosis, persistent referred pain symptoms into the lower leg). Other exclusion criteriaincluded any surgery in the last 3 months, pregnancy in the last 12-months, diagnosed psychi-atric or somatoform disorder, or any other neuromuscular or metabolic disease.

Assessment

All information for this study was collected from participants at an in-person meeting thatincluded: duration of pain and disability symptoms (months or years), age, height, weight, andemployment status over the last 3-months. Further information collected related to activitiespursued in the last month for management of their back pain including medication use, con-sultation with an allied health professional (e.g. physiotherapist, chiropractor, clinical exercise




physiologist) or other types of treatment (e.g. remedial massage, acupuncture). We also col-lected information about the frequency, intensity, type, and time of physical activities per-formed in the last month.

Individuals were classified as performing regular structured physical activity if theydescribed on average once per week for> 30-minutes (in one bout or accumulated over a day)an activity classified at least moderate intensity (� 4–6 METs) defined by the American Col-lege of Sports Medicine (e.g. walking approximately 5.km.h-1 or other cardiorespiratory exer-cise, mowing lawns [18]), activity prescribed by an allied health professional for their backpain (e.g. trunk focussed exercise, stretching), leisure time sport or other recreational pursuits(e.g. golf without a cart), or self-directed physical activity such as resistance exercise.

Self-report questionnaires were subsequently administered at the in-person meeting com-prising measures to examine pathways within the fear-avoidance model.

Disability

Self-perceived disability was measured with the Oswestry Low Back Pain Disability Index(ODI) [19]. The ODI is a 10-item questionnaire regarding how a patient’s low back painaffects different aspects of their life such as walking, sitting, standing, and lifting. Each itemhas 6 corresponding answers that are scored in severity from 0 to 5. The scores from the10-items are summed (maximum total of 50), and expressed as a percentage (0 to 100%).Studies have shown the ODI to have good construct validity [20], internal consistency andreliability [21].

Table 1. Baseline characteristics of study participants (n = 218) and the sub-groups of people identified as reporting weekly physical activity (PA)or no PA. Unless otherwise stated all data are mean ±SD. The types of physical activity and number of participants reporting weekly performance of the activ-ity type are provided. Some participants reported multiple types of activity, thus there is some overlap.

n = 218 PA, n = 68 No PA, n = 150

Age (years) 36.2 ± 6.6 35.6 ± 7.0 36.5 ± 6.4

Female (%) 59.6 73.5 34.7

Duration of symptoms (years) 10.9 ± 7.4 10.2 ± 7.5 11.2 ± 7.4

Height (m) 1.71 ± 0.08 1.69 ± 0.07 1.71 ± 0.09

Weight (kg) 82.0 ± 14.5 78.3 ± 13.0 83.6 ± 15.0

Paid work (%) 68.3 54.4 74.7

Medication for back pain, last month (%) 29.8 19.1 34.7

Regular physical activity (%) 31.1

• Cardiorespiratory, n 30 -

• Trunk strengthening/stabilization exercise, n 35 -

• Flexibility exercise, n 8 -

• Leisure time sport & recreation, n 6 -

• Resistance exercise, n 1 -

Oswestry disability index (ODI, 0–100%) 24.9 ± 13.6 17.6 ± 10.7 28.2 ± 13.5

Pain intensity—current (VAS-c, 0–10 cm) 3.6 ± 2.3 2.6 ± 2.1 4.1 ± 2.3

Pain intensity—worst last week (VAS-w, 0–10 cm) 5.5 ± 2.6 4.3 ± 2.6 6.0 ± 2.4

Anxiety (HADS-a, 0–21) 6.0 ± 3.4 5.4 ± 3.4 6.3 ± 3.4

Depression (HADS-d, 0–21) 4.1 ± 3.7 3.2 ± 2.8 4.5 ± 4.0

Catastrophizing (PCS, 0–52) 15.6 ± 12.6 9.9 ± 10.6 18.2 ± 12.6

Fear-avoidance—physical (FABQ, 0–24) 13.8 ± 5.6 11.8 ± 5.7 14.8 ± 5.3

Fear-avoidance—work (FABQ, 0–42) 11.3 ± 9.8 10.6 ± 9.7 11.5 ± 5.3






Self-rated low back pain

A 10-cm VAS with “no pain” on the left side and “worst pain” on the right side was used tomeasure the current pain intensity (VAS-c), and worst pain intensity in the last week (VAS-w)[22]. The VAS has been found to have good construct validity [23] and reliability [24].

Fear-avoidance beliefs

The Fear Avoidance Beliefs Questionnaire (FABQ) was used to examine patient’s beliefs aboutthe potential harm of work or general physical activity to their back pain [25]. The FABQ has16 items, each scored from 0 to 6. Higher numbers indicate increased levels of fear-avoidancebeliefs. Two subscales within the FABQ have been identified, a 7-item work subscale score(FABQ-w, score range 0–42), and a 4-item physical activity subscale score (FABQ-p, scorerange 0–24). The internal consistency and test-retest reliability of the FABQ are high [26].

Pain catastrophizing

The Pain Catastrophizing Scale (PCS) was used [27]. The PCS is a 13-item questionnaire devel-oped to identify catastrophic thoughts or feelings in relation to painful experiences. The totalscore ranges from 0 to 52 and high scores indicate that more catastrophic thoughts or feelingsare experienced. The internal consistency and test-retest reliability of the PCS are high [28,29].

Anxiety and depression

Anxiety and depression was measured using the 14-item Hospital Anxiety and DepressionScale (HADS). There are 7-items each for anxiety and depression, with items scored from 0 to3; higher scores indicate greater anxiety (HADS-a) or depression (HADS-d). The total scorefor each sub-scale ranges from 0 to 21 [30]. The HADS has good internal consistency [31], reli-ability [31], and validity [32,33].

Data analysis

Multiple mediation analysis was performed according to recommended procedures [34–37] toexamine whether the relationship between pain and disability was explained by fear, catastro-phizing, depression, and anxiety. Highly correlated variables that indicate multicollinearity(r> 0.90), or variables that were not correlated with either pain or disability, were excludedfrom the subsequent mediation analyses based on recommendations for multivariate analyses[38]. Multicollinearity between pain, disability, fear, catastrophizing, depression, and anxietywas assessed by performing Pearson correlations (Table 2).

The following a priori steps had to be successfully met to confirm mediation: 1) pain wassignificantly associated with disability (total effect; c path, Fig 1); 2) pain was significantly asso-ciated with each of the proposed mediator variables (fear, catastrophizing, anxiety, depression;a paths), 3) controlling for pain, each of the proposed mediators was significantly associatedwith disability (b paths), and 4) the relationship between pain and disability was reduced(direct effect, c’ path) when controlling for the proposed mediators (indirect effect, a x b), withthe 95% confidence interval (CI) for the indirect effect of each proposed mediating variableoutside 0 (Fig 1).

A custom written macro (PROCESS; www.processmacro.org) was downloaded into SPSS(v22, IBM, USA) based on recommendations for how to perform multiple mediation pathwayanalysis with bias-corrected bootstrapping tests [34–36]. Bootstrapping is a statistical methodthat involves drawing repeated samples from the data with replacement in order to gain multi-ple estimates of the indirect effect attributed to potential mediator variables [36]. Advantages



http://www.processmacro.org


to using this statistical approach for testing mediation over Baron and Kenny’s 4-step method[39] is that it does not make the assumption of normality for the direct effects, and multiplemediators can be tested simultaneously [35,36]. Furthermore, type I error is reduced becausefewer statistical tests are required [36].

Two mediation analyses were performed (PROCESS, model 4) to examine whether the pro-posed mediators influenced the relationship between VAS-c and VAS-w with ODI. Furtheranalyses were performed (model 4) to examine whether PCS mediated the relationshipbetween VAS scores and fear (FABQ-a, FABQ-w).

We tested for moderated mediation of the entire FABQ model using PROCESS model 15.First, the conditional indirect effects (a x b path) for each mediator variable were comparedbetween individuals who did and did not report performance of a structured weekly physical

Table 2. Correlations (r-value) between measure of disability (ODI) and pain (VAS-c, VAS-w) with depression (HADS-d), anxiety (HADS-a), fear(FABQ-a, FABQ-w), and catastrophizing (PCS).

ODI VAS-c VAS-w HADS-d HADS-a FABQ-a FABQ-w PCS

ODI 1.0 .514** .457** .406** .267** .458** .213** .570**VAS-c 1.0 .680** .260** .137* .292** .243** .580**VAS-w 1.0 .192** .123 .315** .150* .474**HADS-d 1.0 .579** .089 .357** .538**HADS-a 1.0 .009 .223** .374**FABQ-a 1.0 .128 .347**FABQ-w 1.0 .242**PCS 1.0

** is p<0.01, and

* is p<0.05.


Fig 1. Example of the mediation-moderation model tested in this study. (A) is the primary relationshipbetween pain and disability, with the total effect labelled c. (B) are the proposed mechanisms of mediation andmoderation. The direct effect (c’) is the effect of pain on disability after controlling for the mediator variables.The indirect effect of pain on the mediators are the ‘a pathways’. The indirect effect of the mediators ondisability are the ‘b pathways’.







activity session using bias-corrected bootstrapping (5,000 resamples). If 95% confidence inter-vals for the between-group contrast did not include 0 the separate indirect effects for each vari-able were inspected to determine which physical activity group influenced mediationoutcomes. All regression coefficients are presented as the unstandardized regression coeffi-cients (B) from the PROCESS macro. The significance level of this study was p 0.05.

Results

Relationship between variables

All correlation coefficients were below 0.90 indicating that multicollinearity was not present(Table 2). ODI and VAS-c were associated with all variables, and VAS-w was associated withall variables apart from HADS-a. Therefore the only variable excluded from mediation analy-ses was for HADS-a in the relationship between VAS-w and ODI.

Mediation of the relationship between pain and disability

The mediation analyses (Tables 3 and 4) revealed similar outcomes for current pain intensity(VAS-c) and worst pain in the last week (VAS-w), therefore only the VAS-c result will be clari-fied further. The overall regression model showed that 46.9% (p<0.001) of the variance inODI scores was explained by VAS-c and the mediator variables. The relationship between pain(VAS-c) and disabilty (ODI) was significant (total effect, c pathway, B = 3.02, r2 = 0.26,p<0.001). The overall indirect effect for the multiple mediator model was B = 1.50 (95%CI = 0.88 to 2.16), and accounted for 49.7% of the total effect. Indirect effects for the proposed

Table 3. Total effect, direct effect, indirect effect, and r2 values for the mediation models of current pain (VAS-c) and worst pain in the last week(VAS-w) with disability (ODI).

Model Path B 95% CI SE t score p-value Model r2

VAS-c to ODI Total effect (c) 3.02 2.35 to 3.70 0.34 8.82 <0.001 0.26

Direct effect (c’) 1.51 0.79 to 2.24 0.37 4.09 <0.001

Indirect effect (a x b) 1.50 0.88 to 2.16 0.33

VAS-w to ODI Total effect (c) 2.42 1.79 to 3.06 0.32 7.55 <0.001 0.21

Direct effect (c’) 1.07 0.45 to 1.68 0.31 3.43 <0.001

Indirect effect (a x b) 1.36 0.92 to 1.92 0.25


Table 4. Indirect paths of the multiple mediator model for fear (FABQ-a, FABQ-w), catastrophizing (PCS), depression (HADS-d), and anxiety(HADS-a). 95% confidence intervals for the indirect effect were calculated using bias-corrected bootstrapping with 5,000 resamples.

a Path (pain on mediator) b path (mediator on disability) Indirect effect (a x b path)

B SE t score p-value B SE t score p-value B SE 95% CI

VAS-c to ODI

FABQ-a 0.71 0.16 4.49 <0.001 0.72 0.13 5.43 <0.001 0.51 0.15 0.25 to 0.85

FABQ-w 1.03 0.28 3.68 <0.001 -0.02 0.08 -0.21 0.832 -0.01 0.08 -0.22 to 0.12

PCS 3.14 0.30 10.45 <0.001 0.22 0.08 2.80 0.006 0.70 0.30 0.11 to 1.34

HADS-a 0.20 0.10 2.03 0.043 0.21 0.25 0.85 0.399 0.04 0.06 -0.05 to 0.21

HADS-d 0.42 0.11 3.96 <0.001 0.64 0.26 2.48 0.014 0.27 0.16 0.02 to 0.65

VAS-w to ODI

FABQ-a 0.69 0.14 4.87 <0.001 0.70 0.14 5.12 <0.001 0.48 0.13 0.25 to 0.75

FABQ-w 0.57 0.26 2.23 0.027 0.02 0.08 0.22 0.823 0.01 0.05 -0.08 to 0.11

PCS 2.32 0.29 7.91 <0.001 0.29 0.08 3.79 <0.001 0.67 0.21 0.29 to 1.13

HADS-d 0.28 0.10 2.88 0.004 0.63 0.26 2.43 0.016 0.18 0.12 0.02 to 0.49







mediators are depicted in Table 4. Only FABQ-a, PCS, and HADS-d met all criteria for signifi-cant mediation of the relationship between pain and disability. Overall, 42.4% of the variabilityin the relationship between pain and disability was explained by FABQ-a, PCS, and HADS-d.

Catastrophizing as a mediator of the relationship between pain and fear

Because of the similarity in outcomes between VAS-c and VAS-w (Tables 3 and 4), and thatonly FABQ-a was a significant mediator of the relationship between pain and disability(Table 4), we only tested whether PCS mediated the significant relationship between VAS-cand FABQ-a (B = 0.71, r2 = 0.09, p<0.001). All criteria for significant mediation were met (Fig2), with the indirect effect of PCS (B = 0.37, 95% CI 0.15 to 0.62) explaining 53% of the totaleffect of VAS-c on FABQ-a.

Physical activity moderates the effect of catastrophizing

The indirect effect of catastrophizing on the relationship between VAS-c and ODI was signifi-cantly moderated by reporting of weekly structured physical activity (Table 5). Specifically, theindirect effect for PCS mediating the relationship between VAS-c and ODI was only signifi-cant for individuals reporting weekly physical activity (B = 1.31, 95% CI 0.44 to 2.23), com-pared to individuals reporting no weekly physical activity (B = 0.21, 95% CI -0.50 to 0.97).

The conditional indirect effects for PCS mediating the relationship between VAS-c andFABQ-a were not different between individuals who did and did not report weekly physicalactivity (B = 0.37, 95% CI -0.17 to 0.94).

Fig 2. Mediation of the relationship between pain and fear through catastrophizing. Coefficients for thedifferent pathways (a, b, c) are displayed. The indirect effect (a x b pathway) for PCS was 0.37 (95% CI 0.15 to0.62). *** is p<0.001.


Table 5. Test of equality between the moderated indirect effects (a x b pathway) for patients with lowback pain who did and did not report weekly physical activity, using bias-corrected bootstrapping(5,000 resamples).

B SE 95% CI

VAS-c to ODI

FABQ-a 0.24 0.21 -0.11 to 0.73

FABQ-w -0.09 0.16 -0.45 to 0.22

PCS -1.10 0.57 -2.31 to -0.32

HADS-a 0.03 0.10 -0.14 to 0.28

HADS-d 0.32 0.26 -0.11 to 0.92

VAS-w to ODI

FABQ-a 0.18 0.18 -0.12 to 0.59

FABQ-w -0.05 0.10 -0.28 to 0.10

PCS -0.63 0.39 -1.48 to 0.11

HADS-d 0.21 0.17 -0.03 to 0.64







Discussion

Summary of main findings

We conducted this study to investigate proposed pathways within the fear-avoidance model ina relatively large sample (n = 218) of chronic low back pain patients, and to address gaps in theliterature pertaining to the potential mediating effect of catastrophizing on the pain-disabilityrelationship. Moreover this was the first study to examine the moderating effect of physicalactivity on pathways within the fear-avoidance model. The main findings of this study were 1)fear, catastrophizing, and depression explained 42.4% of the relationship between pain anddisability in patients with chronic low back pain, 2) the mediating effect of catastrophizing wasconditional upon the performance of weekly structured physical activity, and 3) catastrophiz-ing mediated the relationship between pain and fear, the first proposed pathway in the fear-avoidance model, and this was not conditional upon the performance of regular physicalactivity.

Fear-avoidance

The results of this study support previous findings for the role of fear-avoidance and depres-sion as significant mediators of the positive relationship between pain and disability in chronicback pain patients [11]. Thus the relationship between higher pain and disability is, in part,explained by higher self-rated fear-avoidance beliefs about physical activity and depression. Anovel finding of this study was that the mediating effect of fear was not conditional upon phys-ical activity. This provides insight into the confusing findings with regards to changes in fear-avoidance following physical activity interventions. While some studies have reported small-to-medium effect sizes for reductions in fear following physical activity or exercise interven-tions for back pain [40–43], a number of studies have shown no change in measures of fear-avoidance despite reduced pain and disability [44–48]. These equivocal findings lead to confu-sion for evidence-based practitioners attempting to understand why a physical activity basedintervention may or may not be effective for reducing fear-avoidance beliefs in chronic backpain patients. Recent evidence suggests that physical activity interventions are only effectivefor reducing high fear-avoidance beliefs when combined with cognitive behaviouralapproaches [49,50]. The results of this study provide support for the need to supplement physi-cal activity interventions with cognitive approaches, because the mediating effect of fear onpain related disability was not conditional upon performing weekly structured physical activ-ity. In other words, performing exercise alone is likely not sufficient to reduce fear of move-ment and therefore pain related disability in people with chronic low back pain.

Catastrophizing

We have also extended current understanding for the role of catastrophizing as a mediator ofthe relationship between pain and disability in chronic back pain patients. Catastrophizing isdefined as an exaggerated negative interpretation of pain that may occur during an actual oranticipated pain experience [27]. There are equivocal results for the association between cata-strophizing and pain related disability in back pain patients [9,51–54], and for catastrophizingas a factor to explain successful outcomes in back pain patients following different types oftreatment [13,47,55,56]. The pooled coefficient from the recent meta-analysis [11] for the indi-rect effect (a x b pathway) of catastrophizing as a mediator of the pain-disability relationshipwas not significant (B = 0.07, 95% CI -0.06 to 0.19), although based on a relatively small sample(3 studies, n = 234 patients) and inclusive of both acute and chronic back pain patients. Ouranalyses of 218 people with chronic back pain revealed that the indirect effect of




catastrophizing, but not fear or depression, was conditional upon reporting engagement withweekly structured physical activity (conditional a x b pathway; B = 1.31, 95% CI 0.44 to 2.23).Thus in people with chronic back pain who reported weekly physical activity, albeit within ourdefinition of physical activity, higher catastrophizing scores in addition to fear and depressionexplained the relationship between pain and disability. Catastrophizing had no influence onthe pain-disability relationship for chronic back pain patients who reported no weekly struc-tured physical activity, with an indirect effect comparable to previous data (B = 0.21, 95% CI-0.50 to 0.97). Therefore a unique and important recommendation for clinical practice is thatpeople with chronic back pain who regularly engage with, or potentially initiate regular physi-cal activity, may require specific psychological counselling or support with regards to negativeperceptions about pain. Because this was a cross-sectional study, the temporal relationshipbetween performing regular physical activity and negative pain perceptions are unclear.

The second objective of this study was to examine the proposed pathway of the fear-avoid-ance model where catastrophizing mediates the relationship between pain and fear. To ourknowledge, we are the first to report that catastrophizing is a significant, positive mediator ofthe relationship between pain and fear in chronic low back pain patients, and that this relation-ship is not conditional on physical activity. While significant, the relationship between painand fear was relatively small (r2 = 0.09). Therefore the relative importance of this pathwayshould be questioned. Indeed two prospective studies [57,58] showed that early changes in cat-astrophizing after injury or following early engagement with a treatment provider for muscu-loskeletal pain do not precede changes in fear, or predict changes in disability or depression.Therefore while a statistically significant finding, the clinical relevance of catastrophizing as amediator of the relationship between fear and pain seems limited.

Implications for practice

Recently the fear-avoidance model has been critiqued for both the lack of empirical supportfor proposed pathways, or consideration for how multi-dimensional processes (e.g. social, cul-tural, environmental factors) influence relationships [59]. For clinicians, the relative impor-tance of the fear-avoidance model is often discussed, but translating research into effectivetreatment for people with chronic low back pain is lacking. Our findings are novel becausethey show that an external condition, in this case performance of weekly structured physicalactivity, explains relationships between proposed belief pathways in the fear-avoidance model.Indeed a strength of our data analysis is that mediation is often thought to reveal specific vari-ables to be targeted with interventions, such as fear and depression. Our data supports currentrecommendations that psychological counselling with regards to fear and depression shouldbe a standard treatment inclusion for people with chronic low back pain [11,49].

The results of our study also provide unique clinical perspectives with regards to the rela-tionship between regular physical activity, catastrophizing, and fear-avoidance. First, peoplewith chronic low back pain who engage with weekly physical activity appear to require addi-tional support to address negative pain perceptions. What this support entails is unclear fromthe current study, although education about chronic pain (e.g. [49]) as compared to the feelingsof discomfort elicited from normal physical activity is a likely first step. Second, it appears thatengagement with regular physical activity is not necessary to influence the mediating effect offear-avoidance beliefs on the pain-disability relationship. While physical activity interventionshave tremendous benefits for overall health and are frequently prescribed in chronic back pain,the overall effect size for these interventions on back pain related disability is small-to-medium[60,61]. Our data suggest that greater emphasis may need to be placed on the psychosocial com-ponents of pain to complement and improve the response to physical activity interventions.




Limitations

There are several limitations that should be considered. The definition of weekly physicalactivity was based on the self-report of at least one session per week for the last month consist-ing of either cardiorespiratory type exercise, trunk exercise (self- or therapist-directed), orother forms of physical activity. This definition does not quantify physical activity in terms ofgross caloric expenditure, nor provide activity ‘dose’ information. Quantification of physicalactivity based on accelerometer data would not accurately capture exercise routinely per-formed by back pain patients, such as a trunk stability program that involves minimal wholebody movement (i.e. accelerations). We did not elect to categorize physical activity based on ahigher threshold, such as three times per week, based on the current low back pain rehabilita-tion literature where one session per week appears equitable to a minimum level likely to havepositive outcomes for patients [60]. Nor did we want to compare different types of exercise,since the overwhelming evidence is that no one mode of exercise is superior to any other forchronic back pain rehabilitation [60].

With regards to the mediation analyses conducted in this study, the explanatory factors offear, depression, and catastrophizing did not completely mediate the relationship betweenpain and disability. There are likely other behavioural factors, such as self-efficacy, that con-tribute to this relationship [11]. However, the scope of this study was with regards to pathwaysdescribed within the fear-avoidance model. While ongoing discussion in the literatureattempts to refine and update this model, we did not measure variables that as yet are not typi-cally included within the fear-avoidance pathways.

The results of this study should not be generalized to all back pain patients. In particularfear about work related activities, as well as depression and anxiety scores, were lower thanreported in other studies of chronic back pain patients. These lower scores may, in part,explain why FABQ-w and HADS-a scores were not identified as significant mediators. How-ever, we believe our sample is representative of the typical patient who chooses to engage withtreatment. Indeed scores for disability, pain, and fear about physical activity were similar tobaseline values for recent clinical trials [47,49]. Thus our findings likely have good generaliz-ability for clinical practice.

Based on estimates for required sample sizes in mediation analyses [17], our study was notsufficiently powered to detect significant indirect effects when the a and b paths (exposure tomediator, mediator to outcome respectively) were small (B = 0.14). For example a small ‘apath’ but large ‘b path’ (B = 0.60) is suggested to require n = 365. Inspection of our data(Table 4) would suggest that we were only underpowered to detect a significant indirect effectfor anxiety (HADS-a) mediating the relationship between current pain and disability. How-ever, further exploration of these pathways is needed.

Finally, while we designed this study to address many of the quality recommendations formediation analyses (e.g. a theoretical framework, sample size justification, accurate pathwayanalysis and inspection of indirect effects, [11]), we were unable to address temporal causalityfor relationships between the respective variables (i.e. physical activity and catastrophizing).This study was a cross-sectional examination of participants with chronic low back pain fromthe local community who attended the University research facility for different experimentalstudies. Therefore no inferences can be made about whether changes in one variable precedeanother.

Conclusion

This study found that fear, depression, and catastrophizing mediate the relationship betweenpain and disability in people with chronic low back pain. The mediating effect of




catastrophizing, but not fear or depression, was conditional upon participants reportingweekly performance of structured physical activity sessions. Thus chronic back pain patientswho engage with regular physical activity may require psychological intervention and supportfor negative perceptions of pain. The effect of fear and depression on pain related disabilitywas not related to regular physical activity, suggesting that psychological interventions arelikely the best treatment choice for these factors.

Supporting information

S1 Table. Self report data from participants in this study.(PDF)


Conceptualization: Paul W. M. Marshall, Siobhan Schabrun.

Formal analysis: Paul W. M. Marshall.

Investigation: Paul W. M. Marshall, Siobhan Schabrun, Michael F. Knox.

Methodology: Paul W. M. Marshall, Siobhan Schabrun, Michael F. Knox.

Project administration: Paul W. M. Marshall.

Resources: Paul W. M. Marshall.

Writing – original draft: Paul W. M. Marshall, Siobhan Schabrun, Michael F. Knox.

Writing – review & editing: Paul W. M. Marshall, Siobhan Schabrun, Michael F. Knox.

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low back pain: the role of fear€¦ · validation of the french version in terms of acceptability,...

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